My approach to sechar va-onesh (Divine reward and punishment) is essentially--or some would say is crudely--a Maimonidean one. Mitzvah goreret mitzvah--averah goreret averah. Good deeds beget more good deeds--bad deeds beget more bad deeds.
I don't like idea of bribing kids. You can make yourself feel better by calling it positive reinforcement, behavior modification, point system, star charts, etc., but you're just fooling yourself. It's still a bribe no matter what you call it.
I'm not saying I don't engage in the practice myself. When literally overnight I had to come up with a way to reorient his davening environment, naturally my first instinct was to dangle some type of bribe in front of him. (Background: David loves to daven and last year he won the "davener of the year award," which happened to be the only year-long award that was given out in his class. He then repeated this feat in camp. But when he transferred to public school he went overnight from singing with twenty other kids in a class room to davening alone in a crowded kitchen as everyone is rushing to get ready for their day.)
However, for some reason it just didn't sit right with me to bribe him to daven. Maybe it's because of my own theological aversion to "slot-machine Judaism" (as I think Leibowitz described it). Or perhaps it's a practical realization that we are going to have to find creative ways to instill in him a love for performing Jewish ritual without the crowd reinforcement that other kids have and if I start now with bribes then there will be no end to it.
In any case, last week I was about to offer him a quarter if he would sit down and daven for a few minutes and suddenly I had an epiphany (or theophany, if you prefer). Mitzvah goreret mitzvah. A good deed begets a good deed. I told him that every time he davens nicely I will give him a quarter to put in a tzedakah cup and this way when we go to shul on Sunday he can put his own money into the pushka (usually I give him change from my pocket).
So far it's worked. Every morning since that day he's been adding a quarter to his cup and this morning he gleefully counted seven quarters. (He was unable to come with me to shul yesterday so he didn't get to empty out the cup yet.) I know it's only been a week, but I hope that his enthusiasm for davening + tzedaka continues. And grows. Mitzvah goreret mitzvah.
Of course davening in the comfort of home and with my encouragement/reminder is the easy part. I have no idea yet where even to begin with encouraging him to be frum in school. When he first started the new school I told him to go to the bathroom before lunch to perform netilat yadayim and say the bracha silently when he leaves. Here I did fall back on bribing and I told him that every time he does it he should tell us and we'll put a star on a mitzvah chart. So far that has not happened once and I stopped asking. Maybe it's too much to expect of a young boy who is still trying to navigate in a "foreign" environment, especially when it isn't his personality to tread a different path. We have to work on him to speak up when he needs to go to the bathroom to pee, forget about going to bathroom not to pee.*
But for now the davening is a good start and hopefully netilat yadayim and more will fall into place. Mitzvah goreret mitzvah.
* There actually is another religious boy in his class and I thought of suggesting to his father that we form a "mitzvah club" for our kids so, for example, they can remind each other and go together to do netilat yadayim. But I can't tell if his father is so concerned about these types of things, which brings up a question for another post.