I am set to do a bunch of things in the coming week and I'd like to leave baby with a babysitter. DH's sister came home for the holidays and really wants to babysit before she leaves next week and I don't want to tell her no, "I don't have enough milk stored up," but I don't!! I hate pumping and can never seem to find the time or desire. I've thought about introducing formula for when he's babysat, but I REALLY don't want to. Is it OK though? I'm afraid he will not drink it or have a bad reaction to it. Is there anything I can do??