How do you deal with grandparents who have different viewpoints on child discipline? It's a struggle trying not to get into arguments!

I think you need to stand your ground and explain to them why you are making a certain decision -- why you do it a certain way. It is very hard at times, especially when they are caring for your child. I had a no screen (tv/ipad) rule for my daughter and my mother made it very clear that she cannot maintain this rule on the days that she cares for my daughter. She does not have the energy to keep her occupied. So we had to arrive at a compromise.