When my children were little, we were separated a few times with various excuses. People always tried to help, and I've never flown separately from my children till my eldest got old enough not to care.

Because I understand how badly one wants to stay with their young children, I always move if asked. And depending on the stress level of the FA (he/she doesn't want to have to take care of an unattended child or have irate passengers), I've found I often get thanked heavily during meal and drink service. I even once got a second seat switch into J after doors closed as a thanks.