go to
www.albertaaquatica.com and ask this exact same question there and you'll get some great answers. A lot of the independent pet store owners post on there and your son will also be able to get some great photos.\
Kevin Guy is bang on about cycling your tank - problem is your son won't want to wait (hell, I don't and I'm over 30).
Some advice would be not to let him name any of the fish for the first few months because you'll inevitably end up with some pretty good mortality/turnover.