It's difficult to advise locations as you don't have a route yet and as I am sure you know the states are HUGE! Also I am not familiar with 'Cool Camping' and I can't remember the places we stayed by name but can offer a few websites for you. We tent camped so limited personal advice on what you're looking for...
The US does leisure stuff really well and govt run sites are pretty roomy and I can't remember a duff one that we went to.
We did stay in 'the floating cabins' at Ross Lake Resort with friends of ours and had a blast. Highway 20 is a beautiful drive too. BUT if you have small children beware - you are surrounded by water and many of the kids in our party fell in. Ours had to wear life jackets at all time when outside the cabin, just in case.
I was thoroughly impressed with their National Park Service. It is great for visiting our National Trust type (historic) homes but they are also the people who look after the huge parks like Yellowstone. (To find accommodation select your State and park then use 'Plan your visit', then 'Things to do', 'Places to go' and 'Campgrounds' - a bit labourious but it's there)
Also check out the State Parks Washington State Parks, Oregon State Parks etc for the other states for their yurts and cabins.
For up to date helpful personal info try the Fodors and Tripadvisor forums. Other people are asking similar questions to you.
New England was fab but I just loved the West Coast. You'll have a ball whatever you decide on.
Shout if you need more help.