I got two of my kids that play with me, 13 and 11 both started playing when they were 10 and i have a 19 year that will play also when she comes up to visit. I always start them out playing at 240fps and put them on my team the first couple of games and I always shoot them myself at the end of the game (especially if they yell out with no hits) if they didnt get hit by a ball that leaves alittle mark. This shows them its not that bad to get hit by a ball if your markers are chrono properly at 280. My friends do this to their kids also and never had a problem with them wanting to play. The kids that we didnt do this to never want to play.
So go out and give your kids a a good pop and they will likely want to play.