Typically I was used to having to have done your first communion (Anglican church), but the minister at my parents church (where I used to be) had a very interesting point of view. He didn't see why it was necessary to deny a child if they wished to participate. That none of us necessarily truly grasped everything in our relationship with God and that didn't prevent us from coming to the table and joining in communion. If the parent is okay with it and the child wishes to receive, he has no problem with them taking communion.
The last couple of times we have been there my daughter has wanted to take communion and he asked if I was okay with that. I didn't feel there was anything to be gained by preventing her from receiving communion (bread, we pass on the wine

)