My son wants a dirtbike. Any help?

My 11 year old son is interested in getting a dirtbike. His mom (my ex) is ok with the idea. So I suggested he look around to see what is available, both new and used. A few of his friends have them and he has discussed his options with them.

I have little/no experience with motorcycles. However, I am a big guy with tattoos/piercings and a long beard. People who see me for the first time thing I am a biker. So going to a motorcycle shop without being prepared would be embarrassing.

Any suggestions? My son thinks a 100cc would be good for him. He also is interested in an automatic transmission, but from my youth I recall a minibike with a centrifugal clutch that sucked.