I don’t let my in laws atch our 14 month old son.  They just aren’t careful enough.  We went to buy a new car so they watched him for about 2 hrs this is when he was about 7 months old.  We went to pick him up and she informed me he ate a blue book mark because she was in the other room and my father-n-law was supposed to be watching him and he fell asleep.  I just won’t put up with that.  My husband sometimes will bring up his parents watching our son and I just say it’s not going to happen.  Don’t feel bad you need to put your sons health and safety first.