I was wondering if anyone else has done this before. So back story  I have started DM'ing for a group of my friend most have kids( two of them are my god sons) and they wanted to help me out so I let them control a few NPC bad guys that the group were hunting, the baddies in question were a thief/bandit group the party got side tracked on. I let the kids control the lackeys of the leader of the gang. What was going to be a throw away encounter turned into a funny/ pretty hard encounter as the kids did not hold any punches, talking about the kids in character as the lackeys targeting the cleric as they were like " hey he heal that guy, we need to get him" then proceeding to wolf pack him to try to take him out.  And after a few lucky rolls on the side of the PCs the kids then have the underlings run as one of the kids said " we don't get paid enough for this" and have them run leaving the leader by himself (lol).

So question as anyone else with kids or DM for friends that have kids ever done this before?

Side note  looks like they want to have a DnD group themselves because the grown-ups are having so much fun and why not them 

No, but that's a lovely story.