I like the idea of a 'customer appreciation' gesture. That said, I would be most warmed by a cookie my child helped bake and a simple cup of hot chocolate or tea. And once or twice a year would be more than enough. Too much and it loses the charm and novelty.
I know some parents suck. I am not a daycare provider, but lets face it, in life some people just suck. And some of those sucky people will have kids....and they will end up in someone's daycare. But...the odd time, breaking the routine with a lovely gesture can smack a sucky person back to reality and make them be slightly less sucky. Or not.