First off God bless you with 3 under 12!
Second Convincing 9U parents they need hitting /pitching coaches? Good luck. I do however agree its needed, just convincing dad, who was all city with the new market mallers in 1987 ( Al Bundy reference there in case you missed it), that his DD needs a coach other than him? That's difficult.
The idea of incentivizing it is interesting but if everyone gets it there is no need to do that.
Keeping a 4 year kid at 10U is very smart. Playing up is WAY OVER RATED. Just play the best competition. If yr involved with the lasers and bandits you already get that.
I think you're on the right track though.