The Southern California Linux Expo and conference has always been a lot of fun when I've attended - and very educational too.
For general conference information, see the official expo site.
Please let us know in advance and we'll see about getting a free, all events pass in exchange for helping out at the booth for a hour. You don't need to know everything about Raspberry Pi, Linux or children's education in order to help. Try it!
Some may wish to carpool. See you there.