D.K.
He may not need a nap. If he is napping and not going to bed until 10pm he isn't needing a nap anymore. My son gave up naps at this age. The tradeoff was a earlier bedtime. I gave him the choice of a nap or earlier bedtime, he took the early bedtime. He was in bed at 6:30 and slept until 7:00am and was very well rested! If he napped or fell asleep he was up until 9pm or 10pm which was very stressful. Most of us moms need downtime at night, so try putting him to bed a lot earlier as if he is outside all day he will be tired, throw him in the bath and then he will crash out! :) If he is that deep of a sleeper then I suggest you decide if you want him up at 10pm or if just bypassing a nap is best. He will adjust after a week to not being so grumpy once he gets the sleep he needs all at once at night. Good luck.