When it comes to involvement as a grandparent,how do you balance in laws vs your own parents? Is it fair to assume that whoever is not working has a greater responsibility?

I think it very much depends on how much either side would like to be involved, and how much you would like them to be involved. Personally, I feel that if it is possible, grandparents should keep to being the "doting grandparents" to the children, rather than as caregivers. That being said, I have friends whose parents are eager to help look after the children and would not settle for weekly visits. For them, it is true that one side is more "proactive" (for lack of a better word) but it seemed to be purely by choice and not by other criterion.