Magilla,
I go along with "Yes".
You might mention to him that you bought a 10yo gasser because that was what you could afford.
You could also tell him that you would only be interested in a place on the Cape and a seasonal site there is 6~K$/season. No Joke!) Then there is the other issue that you can always pull out of the deck. Many of the high end (read snooty) RV resorts will not give a place to a coach over 10yo - if they let you in at all. And that at the beachside is very possibly the worst place to leave it.
Then you can plan tours of the Berkshires. A week North Adams should be nice and also figure out how to leave the fuel tank empty. While this is a really bad idea for the maintenance of the coach, it might do wonders for the relationship when he finds out what is is like to fuel a monster.
Be sure to tell/show your wife (I hate to put her more in the middle of this, but that is unavoidable now) all the things you won't be able to do when daddy takes the coach to the beach.
I wish you luck friend.
Matt - Who has a 43yo gasser