Well, not that you asked for my opinion, but they had plenty of time to decide this and since you already have plans, I would just stick to them. Don't alter them to please someone else. If they had a problem with it they should have talked to you sooner. That was a fairly rude thing to do right before the vacation and since they are only going to be there for one night and part of a day, with you and Teddy, I'd just do what you originally had planned and try to enjoy it in spite of their suggestion not to bring him.