I think therein lies some of the problem. He's stuck with antiquated ideas. You and your wife are partners. I'm sure she agreed to stay home to raise your son, right? Your income is her income as well, and any income she might acquire is also yours, but her time is spent doing something just as important as earning money for the family. The fiance doesn't see it like that. He sees it as you are the only one who earns money, so it's all yours. That's a very controlling attitude for him to have and it's gonna cause them problems in the future. Like I said, just make it some sort of gift, or see if one of those places has some kind of 2 for 1 deal so the friend is getting in "free" without your paying her bill. It's a fine line, I know, but it would show whether he's just doing it because "some other guy is paying" or whether he doesn't trust her. Does he know why you want a friend to go with your wife?