Without a doubt, do your research on the shop and the artist. I took over a week, and lots of hours researching the right artist. Of course, it took me 20 years to finally do what I had always wanted to do as well. So, time and real thought is key. Clean artist, clean shop and friendly service. My thought is, I better like the guy who is inflicting all this pain on me. My relationship with my artist became very important. I trust him. Hes the guy Im going back to when its time to finish my sleeve. Also, once you find the right artist, trust that artist. They should tell you whether that tattoo is going to look good or if it would be better another way, another place.
Good Luck, and enjoy the experience with your son.
Oh, and when its time, make sure he eats a big protein heavy meal. A Fat burger was always my meal pre-session. And get him the darkest chocolate possible, and have him eat bites of it during the tat. Dark Chocolate releases the love endorphines and helps (somewhat) with the pain.