try hair lotion remover, the one that you can use safely on the genital area. or shaving lotion or shaving cream or gel. and use a small eye brow razor, I think a eye razor might be easier to reach the hard to reach places. after use baby oil. I'm just trying to think of a way for you to shave your son without him getting hurt while being shave.

www.goatmountainsoap.com
is a product that is called baby butt crack cream. Is in a small white jar. I hope this helps.

Trim it up with nose clippers?

Yes. Shave it.