The advice I would give is to not assume up front that he won’t enjoy certain things. My husband and I recently went for our first time–I’d NEVER been and he went to Epcot for an afternoon once during a business conference. I planned the whole thing and he kind of went along because he likes me to be able to do things I want to and knows I would rather do them together. We spent a week, did EMH every day, rope dropped one park, closed another every day. He loved it–all of it (and no one was more surprised than he was). We have two more trips planned–partly because he insists that, at the very least, we’ll have to go back when Star Wars land opens.
With respect to M&Gs, obviously don’t force anyone to do something they refuse to do, but in my opinion you should always take it with a grain of salt whenever anyone says they don’t enjoy something they’ve never done. When my husband found out that I wanted to meet the characters his reaction was a mixture of horror and outright disbelief, not only could he not believe I wanted him to do this thing, he couldn’t even believe I wanted to do such a thing. Until he actually tried it–and you know which pictures ended up on his Facebook page and which experiences he can’t stop talking about, right? The character interactions ended up being a real high point for him.
I would suggest you try to at least let him sample the whole experience–and don’t downplay how much you enjoy it or what you’re excited about. My husband said that one of the things he really enjoyed was just to sit back and watch my joy at the whole thing! I hope your trip is amazing!