If you qualify for entrance to the US under the Visa Waiver Program, you should be able to enter and depart the US mulitple times if you do not turn in your I-94 ticket until your finnal departure.

http://travel.state.gov/visa/temp/wi...hout_1990.html

Read the regulations. Not everyone qualifies to enter under VWP without a visa. If either of you have criminal convictions, you must apply for a full B1/2 visa.

Check out www.carrentals.com. If you rented a car in SF (btw - there are very rare weather closures in California/Las Vegas - so don't worry about arriving at LAX and flying stright away to SF) - and then down the scenic Coast hiway to LA, SD, then Vegas and if necessary (if there is a big drop off charge - or for an easier flight ticket) - drive the 4 hours back to LA.

No big deal - pretty straight shot usually - again - except for Friday and Sunday afternoons.

And there is plenty for "kids" to do in Vegas for a few days - including the Cirque de Soleil shows, afternoon magic shows, visiting Hoover Dam, driving out to and maybe hiking at Red Rock Canyon http://www.parks.ca.gov/?page_id=631, and either flying from Vegas to/over the Grand Canyon, or taking a day tour, or even driving yourself and maybe spending the night there. The Grand Canyon is one of the most amazing sights in the world, period.

BTW Dos: The snowfall at the GC is not uswually that onerous, but if a good sized storm is blowing in while you are there - you can still find other things to do in/around Vegas - such as driving over to Zion which is also beautiful, and the roads are usually open. http://www.nps.gov/zion/index.htm

And btw: As suggested - you could also fly to Vegas from SD or LA - as there are many flights, it's short (1 hour) and not that expensive.

Did a quick check of jetBlue fares to Las Vegas for around that time.
From/To San Francisco: $113
From/To Oakland: $103
From/To Long Beach: $47

and up

Weather could be a real factor at New York, Washinton DC, and The Grand Canyon.

Do you have plans for that many days in New York, Vegas, and that many in LA.

You wouldn't need car in San Francisco, New York, or DC. You will need one everywhere else though.

Frankly, if you could arrange this trip in the summer, I think you all would enjoy it much more.
I love the Grand Canyon, but there are so many other National Parks that I find even better. Yosemite and Yellowstone are tops. I even like Zion and Bryce better than the Grand Canyon. That said, there is nothing like your first sight of the GC. There just isn't that much to do there once you've seen it, unless you want to do some serious hiking or rafting.

If I had 3 or 4 weeks, I would pick a trip for just eastern or just western US.

I wouldn't stay more than 1 night in Vegas(especially with kids). Not sure, buy you might have some good fireworks at New York or DC on new years eve. Might have them at Vegas too.

If I were already in Florida, I might skip the cruise and see The Keyes and Everglades.

On New Year's Eve NYC has more than a million people gather in Times Square to watch the crystal ball drop at midnight. Wonderful to watch - on TV. In person it's hell. But there are also fireworks in Central park - which is much more doable - especially with kids.

I like sf7307's itinerary. If possible I would do the Pacific Coast Highway drive from north to south for the better views.

I think 2-3 days in Las Vegas is also fine with kids. Tomsd has given you some good tips. I just did this on a family trip with my brother, mother, niece (14) and nephew (12). We used Vegas as our gateway to the Grand Canyon and then stayed there again on the way from the Grand Canyon to Yosemite. When we first arrived we stayed on the Strip but when we stayed for one night on the way to Yosemite we stayed off-strip at The Orleans. It was a good choice for a family. It's not luxurious but it's fine and it was cheap. It not only had a 12-screen movie theatre but also a full-sized bowling alley. The kids wanted to bowl after dinner so that's what we did. We had a blast.

I would recommend Playa del Carmen over Cabo if you want things to do. There are lots of historic sites and different activities as day trips from Playa. A warning about the swimming pools, however. Most of them around Playa are not heated so the water might be too cool to swim in in January. I don't know if they are heated in Cabo as we were there in early October and they were still plenty warm.

If you're going to Disney and taking a cruise you might want to look into the DisneyWorld cruise and park package. Some friends did this a couple of years ago and loved it. Their kids were a couple of years younger at the time than your kids but they loved it and found plenty to do and LOTS of kids to make friends with although they went in the summer and not the winter when most kids are in school here.

I'd take Belize over Mexico - less internal strife, the people are nice, the Ambergris Cay area is excellent and safe, the diving and snorkling equals or beats your own GBR (especially considering it's not a 2-hour boat ride away), English is the official language (everyone speaks Spanish but knows some English), and your US dollars are usable because Belizeans would rather have US dollars than the local wampum.

There is no way I'd be caught on a train from DC to Orlando, nor would I drive it. LA is way more convenient for driving to Vegas than SF.

I don't think Playa Del Carmen has received any Narco wars violence - but for sure - Cabo has not.

We also took a 3 night cruise out of Miami a few years ago - and it was fun.

If you do get to Orlando - try to get over to the Astronut's Hall of Fame - by Cape Caneveral/Kennedy, and they also have another big space exhibit over there - close to each other. http://www.kennedyspacecenter.com/as...l-of-fame.aspx

The flight simulator is as good as any fighter jet that I have flown in.

BTW - the diving/snorkeling at Cabo Pulmo (halfway between Cabo and La Paz) is as good as it gets for seeing big fish. UC Berkeley even has a research station there. http://tinyurl.com/8t4xsz2

But Belize is also supposed to be great - and off Playa Del Carmen - Cozmel also has some great diving/snorkeling.

My advice is NOT to miss some of the absolutely fabulous National Parks that America has to offer, eg the Grand Canyon, Yosemite NP, Yellowstone NP, Bryce Canyon and nearby Zion NP and the marvellous Monument Valley. These areas are stunningly beautiful. If you plan a visit during autumn a drive through the New England States of Maine will afford you the most glorious vistas of deep orange and red autumn-leave forests. There is much more to America than cities!

We did an almost identical trip last year at the same time as you are going. Had the MOST wonderful time. Not much I would have changed about our itinerary except spend more time in California (and you are already doing that).

http://demansersintheusa.blogspot.co...1_archive.html