Yellowstone is huge. I certainly wouldn't want to try touring the park from one fixed location (not even Canyon). And the roads are narrow and winding, not something you're going to be wanting to drive an RV around on all day. So I'd certainly suggest bringing a smaller car along for the day trips, and having at least two separate campsites for the RV: one based in the southern end of the park (which could also serve as a base for visiting Grand Teton) and one in the northern end of the park.

Be aware that that large RVs aren't allowed on Going to the Sun Road in Glacier National Park. You'll want to check to see if yours meets the requirements to be driven on that road. If not, you'll need to park the RV on one side of the park, and then use your car to drive that very scenic road.

How much time to spend in each place is up to you. I'd suggest spending a week at Yellowstone and Grand Teton, and a week at Glacier.

RV's on the Sun Road in Glacier can not be higher than 10 feet, longer than 21 feet, or wider than 8 feet. You are able to go as far as Avalanche Creek on the west side and Jackson glacier overlook on the east side even if you exceed these limits.
Be aware also that there are FREE shuttles, with large parking areas at the transit centers both on the east side and west side, that will transport you the length of the Sun road.

Yellowstone
I would plan on spending a full day or two in geyser basin around Old Faithful. The better part of a day in Canyon area. You will probably want to spend a day driving thru Hayden and Lamar Valleys. Stop at Tower Falls area and Mammoth area. You might want to spend some time at Lake. If you plan to do any hiking then you might want to spend an additional day.
Depending on what you want to do at Tetons, you probably want to stay 3-4 days there. There is floating on the Snake River, hiking, etc.

You might want to spend part of one day at Jackson(the town).

I would think 3-5 days then in Glacier would be good.

Buy some bear spray if you plan on doing much hiking.

Do you have 2 weeks for those 3 parks or does the 2 weeks include the rest of your trip?

How big of an RV are you renting? For 2 adults and an 8 year old, you could get away with a fairly small one. The compact model I just looked at on cruiseamerica is 19 feet long, 7.5 feet wide - doesn't say the height but I would guess under 10 feet? With that size I wouldn't rent a car to pull behind, you can drive pretty much everywhere with it.

But if you want something bigger you'd probably want a car. Then the price goes way up. If it were me, I'd go with the smallest size and splurge for a hotel room every once in a while just to get out of the RV. But really, I'd price out the cost of an RV (rental rate, gas, RV site cost/night) vs. renting a car and staying in hotels the entire time.

Thank you for your replies. All good information. To answer some of the questions, we plan on renting a 'standard' size RV from Cruise America, so it will be 23 - 25 feet long. And after your comments, we plan on towing a small car for side trips, including the Going to the Sun drive.

Our total trip time will be 2 1/2 weeks so, based on what you're telling me, I'll plan on a few days based at the northern point of Teton or the southern point of Yellowstone, then move to northern Yellowstone for another few days before moving on to Glacier.

Thank you again!

Where are you renting the small RV? Do you have to return it where you rented it? These RV's are sometimes underpowered on hills even without towing a small car. The length restrictions in National Parks include whatever you are towing.
By all means use the Red "Jammer" buses in Glacier NP.

Remember, the red jammer buses are tour buses with commentary which charge a fee. The park shuttle buses are FREE and cover the same road but WITHOUT a commentary.

Don't get the idea that the Red Jammers are the same as the shuttle but one charges and has commentary and the other doesn't and doesn't. They're not the same.

Personally, neither is really for me. I was on GTTS road for 2 days and saw 1 shuttle.

I saw a few Red Jammer tours. I saw one several times and at some of the viewpoints where it stopped only about half of the people got off to look around and read the info boards.

I guess different people have different expectations or desires.

Jammers and the free shuttle are not for me either. However if you are in a motor home that is restricted, and you want to see GTSR, the shuttle is a good alternative stopping at 16 points where you may get on or off along the road. Hard to believe you only saw one shuttle in 2 days. They run from 7:00 am till 7:00 pm about every half hour from the 4th of July until Labor day weekend and move about 300,000 visitors a season.

John,
Apparently over the past few years they've stretched out the schedule somewhat.

However, as John mentions, if you have an over-sized vehicle you really have no choice. In that case I'd choose the shuttle over the Red Jammers as you could get off for several hours at the appropriate stops to do some hikes.

For example, Logan's Pass for Hidden Lake and/or Highlines and TSt Mary and Virginia Falls.

I would think Jammers would be something that I wouldn't like either. That said, we are doing one(although not one on the GTSR). We really enjoyed it when we were in Yellowstone. We did do it in the evening after we were tired from the day, so it was nice to kinda kick back for 3 or 4 hours.

OP has said they are renting a small car to drive around.

If you take the car with you, the trip will be a lot more pleasant. I usually try to get to GT/YST twice a year from Dallas, just to get out of the heat, and my advice is to book your RV camp sites in Yellowstone, now. They fill up fast and are limited. Once you get something arranged there, the others are easier. You may find that you can't get the days or locations you were thinking about in YST and have to do a lot of rethinking to get everything done.

I'm beginning to wonder if mrsdash is coming back to answer any questions or give an opinion on our advice. It's been 4.5 days now.

She replied yesterday at 12:28.