Ugh!!
A.,
My ex mother in law was the same way. As far as she was concerned I didn't know what I was doing, I was too young, blah blah blah. Finally one day I asked her, "How old were you when you had your son?" she said 20, I said "Oh the same age as myself." lol So how do I take advice from a person who herself was "too young" and had no experince either?
We had some words. I stuck to my guns, I was raisng MY son the way I saw fit. If she had advice she could offer it, but she would not continue to undermine me or my decisons.
You know what? She did the same thing to his new wife when their baby was born. She actually called me and told me what a horrible mother the new wife was, on and on, and I told her "This sounds awfully familiar". I haven't heard from her in a 3 wonderful years!
Talk to your husband, hopefully he will back you up and have a sit down with these folks (my ex didn't). Advice is almost always appreciated but being told you are doing everything wrong never is.
Good luck, wish I had more to offer.
W.