Premex:

Based upon your post, I dont think you'll have a problem. Most of the time I've seen "problems" with children flying its been the parent thats the problem.

You might want to try the old bribe technique, I've found it very useful with my nephews and nieces over the years.

One other point, If you get to the gate early, ask the gate folks about arranging a short cockpit visit if the boy is interested, pilots seem to enjoy
giving a quick visit to kids while boarding.