I don’t recommend doing so esp with the age but blow dryers can be set to low cool and be sure you’re keeping it the amount of inches away as you’re supposed to
And maybe not focus on it being super dry but mostly dry to not soak the bed but you don’t wanna dry his hair and scalp out either.
Most blow dryers have different setting like cool and warm apart from just hot air. You can also put them on low or high. But, I personally never use one because heat isn’t good for your hair.