Black hair question...straightening or relaxing?

I don't have a clue, but my son has super tight tight curly hair. He wants it to be straight. I am afraid that it will ruin his hair because it is already so dry. He is 14. What should I do to prep it to be straightened? Should he be using pink lotion or some kind of grease daily? I cut his hair myself because there really isn't anywhere here that does black hair. Can I straighten it at home? I tried to use a plug in straightener, but it didn't go to the root and he looked like a crackhead because it was all frizzy (lol) Yeah, I need advice :) Any help will be appreciated. He has a super high brohawk right now and bald on the sides, well almost bald. Thank you so much. I want to do this for him for Christmas. Oh,and if he doesn't like it straight, all I have to do is buzz it off and it will still grow how it usually does, right?