I havent done a multi centre in the States apart from New Orleans/Memphis but I do know several friends have done a road trip and loved it!
Also internal flights can be quite cheap.

I've had quite a few multi centre holidays in the USA using flights, cars and RVs. Yellowstone is approximately 900 miles from San Francisco and if by touring the coast you mean south down the Pacific Coast highway down to Los Angeles then to visit Yellowstone is adding even more miles to your driving.

My first trip to the USA was over 40years ago when we hired an RV and drove from Los Angeles south to San Diego then east to Arizona, Nevada and Utah visiting Las Vegas, the Grand Canyon and other areas before driving through Death Valley, Yosemite National Park up to San Francisco then back down the Pacific Coast Highway to Los Angles for our flight home. We drove 5000miles and were away for four weeks. We had intended driving to Yellowstone but decided that the additional miles would just be to much driving. Visiting New York, Chicago and San Francisco all need a minimum of two days each , possibly more, to see just the basics and I would advise not to set yourselves too many miles to drive each day in the west as you will end up just spending all of your time at the wheel.

I've visited the USA many times since that original holiday, but touring the west on the open highways all those years ago remains my favourite memory of the country. Hope you have a great trip.

Thank you Judith, I hadn't realised it was quite so far to drive. We will take a similar trip to the one you've previously taken I think, and save up for Yellowstone.

Thanks

Thank you Fiona also

I have heard that it's difficult to get booked into campsites with an RV. What were your experiences with that Judith please?

I think that the end of June, July and the beginning of August when US Schools are on holiday it could be difficult to find a spot. We were there in May and the beginning of June and the only place we had any problems was Yosemite. There wasn't a space in the campground we had chosen and we had to drive a few miles to another. No other problems though.
We stayed in some KOA Campgrounds in the USA and I believe you can reserve sites with them. I'm sure they will have information on the web as will other companies.

Wait till you see some of the RV's, they are like luxury apartments on wheels.

When we hired RVs in Canada and New Zealand we did make a few reservations at different places ahead of time just to be on the safe side if we thought we were going to arrive somewhere late at night after a long day of driving.

Thanks Judith, we will need to travel in the busy times because I'm a teacher and the kids have college. One day we'll be able to go when we want, but till then...

Thanks for your advice, I think we'll try to book.