I'm thinking that maybe your husband is avoiding a discussion about these things because he may not want to have a big confrontation with you. People just don't like drama unless they create it themselves.
My question is this: if he did tell you what was making him uncomfortable, would you listen to him and try to understand? Don't answer too quickly. Would you LISTEN, be non-defensive, see his point of view, and perhaps even change your mind? Or would you flare up with, "How can you say such things? That's so stupid! You don't know anything about it! What's the matter with you, always spoiling my plans?" He's anticipating that you will flare up - so why not just keep the peace and let you do what you please?
He may be feeling toward you the way you feel toward him right now.
In a real conversation, somebody has to do the listening... and since you're the one who wants the information, it's going to have to be you.
Husbands sometimes have different insights on their wives' friends - insights that the wives would never think of. Wives certainly are that way about their husbands' buddies.
I think you probably should have consulted with your husband about taking care of the children for the convention night before you mentioned it to your mother or anybody else. Otherwise, it has him feeling like a hired hand. You and your husband need to be on the same team.