Rescue dog bit our 2 year old

I know this has been posted before but I am at a loss. We have two dogs. Both are rescue dogs from before we had kids. One has always been aggressive but seemed okay with the kids. We have told our caregivers to watch them closely and not leave them alone together. My mother-in-law was watching our kids today and when she went to put the baby to sleep, the dog bit our 2 year old in the face! I want to rehome the dog. I’ve talked to a friend that rescues dogs and he believes he can find a single older person that would love her. My husband thinks we should just keep them separate but I don’t know if that’s possible. What would you do?