I've BTDT w/ both sides of our family, and I tell ya, it stinks. Dh's family was much easier to talk to about things than my family though. (my mom still has a switch/belt sitting beside her chair for my sister's kids.: ) What we did was one day when dd was born I just told them-you are NEVER to hit or discipline our kids. If they need discipline either dh or I will do it. I let them know pretty quickly that if they ever hit our kids that would be it for our relationship. It was hard to do, but my kids are more important than me feeling weird about it. Luckily for us, dd has never been there when my sister's kids get hit, so we haven't really had to deal with it.
However I have always let it be known that I don't agree w/ spanking, and have no qualms at all about engaging my sister and my mom in a "debate" about spanking.I have actually "won" my sister over to not spanking, just by being an example to her. (although she still lets mom hit them-whatever!) So maybe if they observe you showing GD, maybe someday they will follow suit??? One can only hope.But yeah, I agree-I would NEVER leave your child alone with them-EVER.
However I have always let it be known that I don't agree w/ spanking, and have no qualms at all about engaging my sister and my mom in a "debate" about spanking.