hi stung,
i tried behavior modification incentives/punishments with my ex and they NEVER worked to do anything other than give him another reason to drink and blame me. i learned in alanon and therapy not to do behavior modification because it isn't healthy for you and doesn't work on them. someone who knows more about it can explain why, but that is something i learned the hard way years ago.
that sounds like a great idea to do something that benefits the kids and your family as a whole. very positive approach. you are way ahead of where i was back then.