The Albatross is ideal for this. Sizable fuselage for comfort as a living space and enough places to fit lav, shower, kitchen, etc, big enough to stand up in, tri-gear so it's level, and amphibious to open up new possibilities for destinations. It's been done several times, most famously by Jimmy Buffett.
I've also seen amphib Caravans at Oshkosh that lack the full RV treatment but are large enough to cart along all the camping gear you'd ever want. I camped near a Turbo Commander in the North 40 one year that similarly had everything including the kitchen sink inside, to be spread out for camping. They even had a big-screen TV that they put out in their campsite to watch flying movies in the evening.
If you really have money to burn on this, a
Lockheed-Martin LM-100J, which is an extended civilian version of the Lockheed C-130J Super Hercules, is probably the best way to burn said money. In fact, you could either outfit the plane as a giant flying camper, or better yet, you could just put a travel trailer, a boat, and a nice dually diesel pickup inside and go where you wish from the airport. Unfortunately, the cargo compartment isn't high enough (10') to accommodate most of the bigger motor homes.