Hi Herb,
So, is the boat name "official"? For summer wandering and cruising, I have to go with Roger's suggestion of the Pacific Northwest. We did that for two summers and barely scratched the surface. If it wasn't for the 9 1/2 months of "The Rain Festival", I would consider moving there. In my opinion, the finest cruising to be had in coastal US.
I don't have any hands-on with the RVing there, but an hour with the Trailer Life Campground Guide would give you a gazillion options.
The San Juan Islands, north the the Gulf Islands in Canada, across to Victoria on Vancouver Island, south in Puget Sound to Seattle (what a great city!), further south to Olympia. I get excited just thinking about all the possibilities.
If you want something on a smaller scale, there is a lot of water to had in South Dakota, Montana, and Wyoming... and cooler summer weather. The Missouri River is dammed in the Dakotas, making for some huge lakes and lots of shoreline to explore. Trace the route of Lewis & Clark. Drop down into Wyoming and explore Yellowstone and the Tetons - plenty of RVing and boating. You'll be at the 6,000-8,000 foot elevation, so cool nights and crispy days.
Lake Powell is absolutely magical, but (as Dr. Bob said) it is HOT there during the summer. September is great there, and could be on your route from either of the options above. Then back to south Texas for another helping of great weather for the fall.
Give me a call and we'll get together and swap some more stories.
Best wishes,
Jim