Us kids is the only way to go. They have a program where every 6th club is free. the clubs are very nice and don't break the bank either. My boy is 4 (will be 5 in august), and he swings the yellow ones. I have a Ping Moxie putter for him though...
Once they are a little older, I'd check out Flynn Golf until they are strong enough to swing real clubs.
If they are swinging something too slow, it's only training their body to swing slower. You want them swinging as fast as possible as a kid. You can always teach direction when they get older.
Having Fun and and teaching speed while they are young are the ticket.