quads, boating and camping. Hmmm....
I have seen trailers where they added a second story to a boat trailer and had PWCs stored high. Hydraulic system would lower the top rack once the boat was off. You might be able to do something similar to store quads up high. Clearing the tower might be a problem though.
Camping and boating is best done with a motorhome. If your truck has a full size bed you might get by with a slide in camper.
I know people who tow two trailers. One is a truck driver and claims that it is okay if you have the commerical truck license. Another one just does it and says he has never been stopped or challenged, but he doesn't do it very often or go very far.
Towing two trailers will definately be a hassle. Forget backing up. Pulling into gas stations could be an issue. The people I know who have done it have always towed a heavy and a light trailer, such as a ski boat followed by a PWC, or a camping trailer followed by a light runabout. A toy hauler followed by a 3000+ pound wakeboard boat could be interesting.