Advice for 6week road trip in the USA in winter with kids

Hi we would love some travel advice.

Me, my wife, 3 year old and 9 month old are planning to visit the USA for 6 weeks in December and January and are looking for some suggestions of where to go.

2 years ago when there were just three of us we flew to Oregon and did a road trip up troute 101 to Olympic National Park and Crater Lake visiting Seatle, Portland, bend, and a whole bunch of places in between. We loved the trip and are going to stay for an extended time this year.

Ideally we want somwhere warmer than the UK, a road trip, stuff to keep the kids entertained and to do some national parks.

Can anyone help with some suggestions?

Cheers

Are you looking for someplace warm? Maybe some of the Southwest parks in Arizona and Utah,, like Grand Canyon South Rim and Zion? Bryce could have snow and you would probably have to rent a car with AWD or snow and mud tires, since you are not supposed to use chains on rental cars.
You could fly into Vegas and pick up your rental car there.
Or you could add in Death Valley.
California has some nice national parks and don't overlook state parks, like Jedediah Smith State Park which IMO is superior to Redwoods National Park.
Maybe Florida, Everglades and the Keys?
Any other interests?

Well warmer than the UK in December/January shouldn't be so hard. Head south, and your best hiking will be the south west - but that's not to say it won't be still be cold - especially if you are thinking about places like Utah.. At that time of year I'd look heavily into New Mexico, Arizona, and Texas ( the first two would be my choices). or go southeast and try Arkansas, Louisiana, or Georgia and the Carolinas.

Personally I'd recommend New Mexico.

IF the weather happens to be cooperative you can go a bit north too. But I'd count on it being cold most of that time.

The Southeast is great for road trips and there's plenty of kid friendly stuff to do. As someone who grew up in South, lived 12 years away, and am now rediscovering it in my 30's, I could write paragraphs, but I'll try to keep it manageable.

Favorite cities: Asheville, New Orleans, Memphis, Atlanta, Charleston, and Wilmington, NC.

Favorite small towns: Natchez, MS, Eureka Springs, AR, Bentonville, AR, and Fayetteville, AR.

Favorite Kid Friendly Attractions: Georgia Aquarium in Atlanta might be the best aquarium in the world (has a whale shark!), Memphis has one of the best zoos in the country (pandas!) and kids really like the Peabody duck march, New Orleans aquarium, the City Museum in St. Louis (not technically the south but it's close and there's no other kids museum in the world like it), and Crystal Bridges in Bentonville is free and might be one of the top 3 art museums in the country.

National Parks: Great Smoky Mountains in Tennesseee/North Carolina, Mammoth Cave in Kentucky, Hot Springs in Arkansas, Congaree in South Carolina, and Everglades in Florida.

Feel like Google Images can let you take it from here!

Thanks for the suggestions its very helpful and we have some more research to do now!

Our emerging plans, which we may change based onome of the suggestions, was 2 weeks in Hawaii, fly to San Fan, Napa Valley, Yosemite and surrounding area, gradual trip to Las Vagus then fly home.

Need to look again at south east USA, mya asumption was it was pretty build up compaired to the West coast but will look at it again.

Any more suggestions are very welcome