I think Gold Beach at the mouth of the Rogue River is your resort town. There is a road from Gold Beach (through Agness) that hits I-5 just north of Grants Pass.
The headwaters of the Rogue are actually within Crater Lake NP.
Highway 138 west from the north entrance is alongside the Umpqua River for many miles on the way to Roseburg.

Are you doing this trip for you or the kids?

To bbqboy: both,(or I guess I should say all, since my dh will be there, too). Why?

One other thought: there are Giant Redwoods down by San Francisco too. they are on the other side of the Golden Gate Bridge from San Francisco. They're in Marin County. This way, you wouldn't need to drive down the coast from Florence, just to see the Redwoods.
I'm not really familiar with Gold Beach. I know that every time I head to the coast in the summer time, I freeze! I've heard good things about Canon Beach too.
I thought you wanted to take the train, so I looped you back up that way. You can certainly drive all the way down. That's an option too!

Sorry if I was confusing. I guess what I meant to say is that taking the train was an option, but had it's pluses and minuses. I think I would prefer to drive so that we can see more, but the drop off fees could be a problem in SF. The train trip sort of sounded like fun, in theory, but I am not reading very good reviews. I think the first thing I am going to do tomorrow is get a good map of Oregon and California. Hopefully, that will help me with the geography involved. Thanks so much for all your advice and suggestions!

MJ, the reason I asked is that kids have different priorities.
We did the coast lots when my kids were younger.
Astoria and Seaside yes, Cannon beach no.
Stuff that adults find interesting aren't necessarily the same
for kids. I wish you could be in Ashland for our July 4th parade, for example.
Hours long drives through stuff that adults may find romantic=boring to kids. Just my thoughts.

If the drop off fee in SF is $400 or less then turn in the rental there.
The Amtrak fare for 2 adults and 3 children from Portland to San Francisco is $422. (10% discount for AAA members).
There are 2 Fodorites that never have anything good to say about Amtrak. If your train into Emeryville arrives 2 hours late you are still in San Francisco before noon.
On more than 1 occasion I have arrived in Sacramento on the southbound Coast Starlight 30 minutes early.

bbqboy--Even kids don't always agree on things. Ours cannot stand Seaside and they are teens. We do Cannon Beach instead and have for years.

bbqboy-- your point is well taken which is why I am asking for help and suggestions as to where to go to balance all the interests involved. I do want my kids to see another part of the country and what it has to offer but am certainly aware of their boredom level if all we do is drive and site see.

Hence why I asked about the Florence area (with the Sand Dunes) and the Rougue River Trips-- all will most likely enjoy that. My kids have all mentioned the giant Red Wood trees and my oldest really wants to see the one you can drive through. We usually spend much time camping on the Ocean with little to do but paint shells and swim and I find that my kids have a great time. If they can swim, they are happy. Pools (especially one that there Dad and I can pull up a lounge chair next to) are ideal.

BTW: if any of you are near the coast this morning, please stay safe.

MJ, that's why we always liked Neskowin. A creek flows though
away from the actual beach (and wind). Fun to make sand castles and stuff like that.
As far as Seaside vs. Cannon Beach, my kids loved the boardwalk
as opposed to the Shops at Salishan. Just Saying.
They loved hiking up the Astoria Column. They dug the Darlingtonia wayside.
Many places to stay in Ashland as a base, Bard's Inn for one
has a pool and is right Downtown.
You could hit the Rogue, Crater Lake and Jacksonville
from there.
The Green show before Shakespeare is fun(and free).
http://ashlandchamber.com/index.asp
http://www.abbnet.com/
It will be warm in sunny in Southern Oregon in July.

The drive=thru tree is on the north coast of California, not near San Francisco.
Both Ashland and Jacksonville would make a great base for Southern Oregon sites. Check out both town websites and hotel listings and see which one suits your family better. I like things about both towns. It depends on your family.
I'll be away from my computer for a few days, so I won't be able to answer anymore questions until next week. Have a good one!

I found Seaside to be a bit cheesy, like one of those Jersey shore boardwalk places.. but children like that sort of thing. There are shops and galleries galore in Cannon Beach, with Haystack Rock which is really the star of that show.
Tide pools etc and then lunch outside at Mo's ..

We lived in Portland and found the 2 and 3 day minimums in the hotels annoying. One September, we drove down to Arch Cape and spent a couple of nights at the Inn at Arch Cape which was wonderful. Fireplaces in all rooms and cozy, with closets full of games and books for kids of all ages, you can eat outside.. it is a great honeymoon or family spot. With tiny kitchens if you wanted to get take out and eat there or have breakfast before leaving in the mornings.
You can walk to the beach from the Inn, it is on the same side of the street, just a stones throw from the ocean.
www.innatarchcape.com

bbqboy--You do realize that Salishan is not in Cannon Beach, but quite a bit further south?

same to me. my kids weren't interested.

My kids preferred Seaside to Cannon Beach but mostly because there was a carousel and an arcade/pizza place. We enjoyed both towns with the advantage going to Cannon Beach (for shopping, art galleries and dining). But, mostly we spent our time exploring the beach, hiking, trying to find the best pie. We were in Seaside for a family gathering for a week, staying at a timeshare and explored as far south as Manzanita but we mostly stayed in the same area.

I like the suggestions you have been given so far for traveling south.

I would not take the train unless I had to.You can just see so much more taking the car. I am taking the train from Seattle to S.F. myself next month.They often do arrive late.One thing you should know is that unlike east coast beaches swimming is not usually the highlight of a trip to the coast.It is not easy to see the coast and Crater Lake.May I suggest:
first morningrive to cannon beach and stay one night
second night back in Portland
Day threerive to Crater lake
Day fourrive to coast either following Rogue River or heading directly to Crescent beach and then spend your remaning time driving the coast route to S.F.
For the most part, driving I-5 in California is a real bore.

I mentioned the train option primarily to avoid the drop off fee problem. After you go over the Cascade Summit SE of Eugene, you will not see much scenery because of darkness. If you can sleep on the train, you will wake up as the train is pulling into Sacramento about 6 AM. Even if the train is late, It will not spoil your day if you don't get into SF before noon.
Driving I-5 between Medford OR and Redding CA in daylight is not boring. Mount Shasta is a beautiful view. From Redding south to Sacramento can be boring at times.
I have been known to ride the train overnight, get off in Sacramento, ride the YOLO bus out to the airport and rent a car from there. I do this to avoid driving a slippery I-5 with my own car.

The train sounded like a wonderful adventure at first, but has quickly become something I am trying to avoid. I only feel compelled to go to the coast of Oregon because the sand dunes sound like fun. Otherwise (and as was orginally planned) we would be happy staying away from the coast in Oregon. We had orginally thought we would love to show the kids (who are used to Disney and such) some National Parks, or at least things they don't get to see here in the North East. All I really know right now is that I a family of five that will be starting out in Portland and Mt. Hood and leaving from San Francisco. I would like for all to have fun along the way, knowing it will require some form of transporation along the way....

All of your opinions/options/peices of wisdom are greatly appreciated. Any more imput is also welcome!

mjkre, I'm really interested to read this thread since I'm doing the reverse of this with my two boys (ages 6 & 9). So we are really the same, but in reverse ;-) I'll be doing this drive from SF to Portland in early May. We have some friends we are visiting along the way (in St. Helena, CA, then again in Albany, OR, so our route might be slightly different) and we are camping, but I'm more than happy to share any highlights my boys loved with you since although our kids are different genders, they are the same age range.

Wanted to suggest Out N About Treesort in Takilma, OR for a fun family adventure. http://www.treehouses.com/ There is a zip line activity on site & a swimming area & horseback riding & other activities. Staying up in a treehouse or a yurt. How different & fun. Stayed 2 nights in Oct. few years back great!