Twy,
First off, traveling in an RV is NOT CAMPING. If where you sleep has heat and indoor plumbing, that is not camping. It is just a small motel that arrives when you do. If it has a usable dinette (many do), then daughter can sit there and entertain herself with books and games.
I advise you to look at all the RVs you can find. Particularly work Craig's list and other local sales. If you can find used, you can save a lot of money. Just be very cautious of anything with square corners in the roof. Roof leaks can destroy any RV in an amazingly short time.
You don't say what the boat is, but I can tell you that our antique 23' A has about the interior space of a 30' sloop or a 28' powered boat.
Do you know the difference between an RV and a Boat??
Water can leak out of an RV.
Matt