I've been a Carer for 8 years however not family. We always acknowledge the children's family. We look at photos talk about them and let them know their parents love them but can't look after them. We answer age appropriately and with what we know. They will miss their mum and love her always. I don't know your circumstances but we would say things like" mum and dad can't look after you as they find it hard to keep food in the fridge" etc. if you have other questions feel free to pm me. Good luck to you all quite often childrens first placements are the most difficult as they grieve. Get angry. Blame themselves. Feel guilty that they are enjoying themselves all in one. Such a beautiful thing your doing