We started running family LARPs at Origins (a big gaming convention) when our daughter was six years old.
We'd been going to Origins for several years, and the activities we could do as a family were pretty limited. There was usually one miniatures game involving My Little Pony, and one person running life-sized Candyland. My daughter loved those, but she also loved roleplaying and LARPing (live action roleplaying). She'd just had a birthday party where I wrote a LARP for her and her friends, and had fallen in love with that form of roleplaying.
We saw other families in the same situation at Origins, so we decided to run what we'd love to play in, family oriented LARPs.
The first year we ran a couple of time travel family LARPs. The kids played a group of kids who got mixed up with an eccentric inventor and were traveling in time. The parents played the NPCs and villains. One scenario that first year was travelling back to help Annie Oakley win her first shooting competition, and the other was travelling back into pirate times to make certain history stayed on track.
We had Nerf guns for the Wild West scenario, and foam swords for the pirate one. The kids and parents all had terrific fun, so we kept running new kids LARPs year after year.
Eventually we started running LARPs that involved more thinking, and those stories evolved into the ones you'll find on Detectives Guild.