What is your opinion of my mother in law asking me to stay with her on weekends? Is she asking for too much?

The grandkids should be watched by someone else if your MIL is at school and your FIL is not feeling well. You shouldn't have to give up your weekends to babysit someone else's kids! You could offer to go over for one weekend but other people should also help as well. Given your father in law is on meds which is making him feel bad he should be fine once the meds are finished. I can't see him being on meds the entire summer. Even if he is I agree asking this of you for the entire summer is asking far too much. This is her husband and grandkids so if anything she should just postpone her course and take it another time. You can help out one weekend and your husband another...it is his father so he should help even if he doesn't want to. There must be other friends and relatives as well. Why are the grandkids there being cared for on weekends? The parents of those children should try and find someone else to take care of them since it is causing a big problem for your in laws.