An Rving grandma here with an eye towards your sanity: unfortunately, the size of the trailer you really need, will require a larger tow vehicle. I'm thinking of kids/toys/crafts/books, etc - the general stuff that comes from raising a family. You aren't going to have the storage you need in a small B or C. You will definitely want an RV with a slideout, the bigger the better. And bunkbeds - making up a couch or dinette into a bed daily, will get old really fast.
I agree with others - if you can find a park model trailer in a non-senior park, would be ideal. Otherwise, if I had to pick an RV where you get the best bang-for-the-buck for a family of 4 extended living, I'd have to go with a 5th wheel. I drove ours all the time, and it was NOT scary at all. The other option would be a 28-30' Class C, and then tow a smaller vehicle. You are about the same length overall as a 5er; but for running around and sightseeing, a toad is a nice thing to have. A large popup camper might work, but your storage (and privacy) will be limited.