Can a child join Salat in family?

Young Children (say, about 5 years old) do not have the obligation and are not supposed to join Salat; they are not fully able to understand the meaning and to do everything properly but they like to be part and imitate what they see. Is it allowed/well-received to let them participate in the way they are doing it? If not, should they participate under age when they want and learned to do everything properly (e.g. 8 years old) Answers according to any fiqh are welcome, Hanafi preferred.