I am potty training a 2 1/2 year old and he won't pee in the potty.?

I work in a daycare and am in the process of potty training my 2-3 year olds. Their parents are "sort of" helping at home. We are so patient and doing so well, but I have one little boy that will "sit" but then get very cranky and cry. We try to console him and talk him into trying a little longer, but he gets so upset that we let him up to wash his hands. He always waits until his pants are pulled up and then he pees in them. Sometimes he makes it back to his cot or chair before he does, but most of the time he will pee 30 seconds later while washing his hands. I asked him if "it hurts" and he said no. We tried to hold a piece of toilet paper against his penis to feel like underwear, but he will not pee in the potty. I am not frustrated...I'd rather see him pee his pants for a while longer if it would keep him from getting a bladder infection from holding it too long. But I would like some ideas/tips if there are any out there. Thanks for your time!