babies do get hurt especially when just starting to crawl and walk. so if he fell on her watch don't get to upset because he may fall with you next. but if you feel she is to elderly to watch him then just tell her that he is a handful and you feel she may not be able to handle it but you still want them to spend as much time together as possible. set up lunch dates for you, her, and the baby. invite her over for dinner, go to her house and offer to clean it while she plays with the baby, or make her feel like you need her help. invite her over to watch the baby so you can wrap some christmas gifts. you'll be in the same place as your son but can get some stuff done and she gets to spend time with her grand baby. honestly if she has fallen several times and can't get herself up do you think maybe you should offer her to move in with you and your husband for her safety? if that was my parent i would.