How strict should you be about insisting your kids stick to things that they've chosen to do? My DD has tried 4 activities in the last 18 months - dance, Rainbows, gym and now karate. DS#1 has fairly consistently enjoyed cricket and karate so I know that it will only take a bit of nagging from us to make him agree to go and he'll enjoy it.
But how strict are you when it comes to these things? They have to go to school but these are voluntary so I don't like to insist too much - but then again it's a bit pointless trying to improve your skills and get picked for teams/gradings if you keep missing sessions. I have friends whose DD's have something every night - can't imagine how she manages that without rows.