I was in this same position about two years ago with both my parents and MIL. I agree with trying to keep situations on your turf if at all possible, but for the first year and a half that was almost impossible for us. DH agreed with me, but still left most of the interactions between grandparents to me.First, I was always present when grandparents were with DS - I would kindly but firmly correct them when I saw things heading in a direction I didn't care for and several times removed DS and myself from their presence when I felt interactions were very inappropriate. No words, just scooped him up and took a walk, drive, ect. Second, I had to eliminate any second guessing as to what anyone else thought about what I was saying or doing. This is your dear child and you are the voice. Don't worry about how you are being judged by family, you are doing what is right. If you are met with hostility from MIL, remove yourself and your child until she comes around. I had to do this with my own family, and believe me, they learned how to treat my child appropriately in order to spend time with him. Stick with it.