It really doesnt matter either way. The females will get larger than males but not by very much. Most ball pythons will stay under 4 feet long. Both genders take to handling very well. I would suggest just check out a forum and ask questions. The right forum can be a great place to learn how to care for a snake properly. Check this forum out.
http://www.redtailboas.com/forum/. As a parent I would join and ask questions that you seek answers to. I know it is a boa forum but there are many ball python owners/breeders that are members. We are a very family friendly forum. I have an 11 year old daughter and I have no problem what so ever showing her some threads and pictures there. No cussing is allowed. I hope to see you and your son on the forum. It is a great learning tool. I hope this helps.