I have always thought hey those things use a lot of fuel, can't be much fun to drive and then you got to pay about what you would pay for a hotel room to park them in what amounts to a trailer park crowded with people. So you spend a ton more on fuel and still pay to park them, and they cost thousands, if not 100s of thousands of dollars. They don't make sense to me at all. Sure if you spend a LOT of money they are kind of luxurious but never made any sense to me. I like camping, and want to go someplace where I won't see anyone, you know experience nature, not other drunk people. But you could likely fly places, rent a car, stay in the Ritz for a lot less than what it costs to buy and run a motor home.
But back to the original question, I say rent an RV for a few weeks, then Charter a sailboat for the same amount of time and see what the family likes.
There are many... MANY... variations of RVs. I totally agree with you on most points. But "RV" doesn't only imply a Class C Motor Home with marble floors that looks like the Dave Matthews Tour Bus. But holy cow, there are RV's that are nicer than some houses I've lived in.
For my purposes, I've always been interested in the Rialtas (no longer made) which are just a tiny notch above a conversion van. I'm talking about RVs that you could drive through a take-out window at a fast food joint. These are basically large vans with a real bathroom in them. The rolling equivalent of a 25foot sailboat.
My Ford Expedition gets 16 miles to the gallon while my Hyundai gets 25. But anything over 6 hours on the road and the additional comfort (and room) of the expedition far outweighs the gas savings of the little car. Still, there are small RVs that nearly rival the fuel economy of my Expedition and you can actually lay down on a bed and use a real bathroom- or take a shower if you are off the grid.
I have no desire to trade Hampton Inn for the KOA campground for all the reasons you mention, which I completely agree with you.