Recruitment Award for my efforts running kids D&D for our neighborhood kiddos. We've had 7 kids in our kid's game (now being DM'ed by a neighboring dad), 3 more kids on the way, and a splinter group of older kids that are building their own Pokemon-based RPG. A few of the 9 year olds are in our weekly adult game.
Gaming with kids is awesome. One thing I noticed running kids through classic modules, it's a chance to reconnect with those amazing places you visited yourself when you were a kid. The Keep on the Borderlands or The Lost City might be old-hat to your adult gamers, but it will be awesome to the kids; I'm a big believer in the shared experience of modules. In this case, you can trade war stories across generations.
There are a few selfish reasons for starting the kids young, too. Recruiting players may be hard - so make your own with the neighborhood moms, dads and kids. Recruiting is DM job security! Plus - I've noticed that if some of the adult gamers are bringing the kids to the game, it's a little bit easier getting time away from the spouse - gaming is a family activity instead of a "Dad" activity.
You'll hear some funny stuff at the table, too, and the kids will try some pretty entertaining things. For a while, ours all went to the Looney Tunes school of tactics.
Here's an older post on things you might hear yourself saying when dungeon mastering for 9 year olds.