ARG. I had a bad feeling about having a family member fill this role. I do not want to have to "manage" my father-in-law!
My mom was a big influence on my parenting style, in that I often ask myself, "What would my mom have done in this situation?", and then do the opposite. But when we needed a nanny when DW decided to go to school, and DD was only about 6-8 months old, my mom stepped in, and it worked out wonderfully for all involved.
DW and I are huge proponents of consistency, and so, before we ever agreed to let her watch DD, I had a frank talk with my mom in which I indicated that the only way this could possibly work is if she got on board and did things OUR way. She did.
Every day we'd talk endlessly about every detail of DD's life, and how we react. I could also tell when something was going on that was different, because DD would indicate it with her behavior. For example, I remember her sitting up at the entertainment center, slapping her hands on the glass doors, and looking at me like, "Hey, do you see me? I'm hitting this. What are you going to do about it?" So I asked my mom, who told me she'd told her not to, and I said we just let her, she can't break the glass.
I suggest it would be a good idea for your DH to have a similar conversation with his father, and the sooner, the better.
