Bewildered: I understand that your husband is upset, but you have drawn very reasonable lines and applied them to everyone invited. You even went the extra step of finding a babysitter so you SIL doesn't have to. Your SIL should have realized by now that adult receptions are hard on small children, and small children at receptions can be hard on adults trying to celebrate adult events. If you give in because your SIL is throwing a tantrum worthy of one of her small children, you will begin your marriage by establishing that she can throw a fit and get her way. If she is the only one allowed to bring small children, everyone else will wonder why THEY had to leave THEIRS at home. Stand your ground; she'll either get over it, or she'll stay home watching her children while the rest of you celebrate an event *with the rest of "her family"* that she should be celebrating too.