Q: Do we need to pay sadaqatul fitr for children ? Wife?
A: A father having the nisab (minimum requirement of money to start giving zakaah) will pay it for his children that are not yet mature.
He can also deduct this amount from their savings if he is not doing very well financially. However, if he is generous, and he gives it from his side, the reward will be greater for him.
If the wife has her own money, she will be responsible for her own giving. He can also give for her, should she give him the permission to do so.
Allah Certainly Knows Best.