I'm a child care provider and my first questions that i thought of is... Are the other children at the child care potty trained? Is this a new environment for him? How does the provider handle his accidents? Is he looking for more attention from the provider?
Sorry for all the questions just trying to better understand. As a provider we have certain times that everyone has to "try" the potty. This helps with accidents b/c children usually dont like leaving an acitivty to go the bathroom. So we go before going outside, before rest, then again before afternoon outside time.
I'm not sure what else you could do. You seem to be on top of it and trying all the tactics. Can you provide the care giver with special treats to give for "non" accident days. Stickers are always good. Keep a chart at the child care.
I dont think i answered your question to much but maybe gave you things to think about!