G.♣.
I would do it when he's asleep. My son has really chapped hands (lots of hand-washing - very dry, cold air), and I've been putting Aquafor on them. It works great! As long as he doesn't rub it all off. So I started waiting until he was sound asleep. I just tip toe into his room, rub in on his hands and tip toe out again.
Give it a try!