Hi Chris and Matti, and welcome to the forum!
What an exciting learning experience for you to enjoy with your son. You may have already found these links for yourselves, but in case you haven't, here's some great introductory material from the forum to get you started in the right direction:http://www.aquariumadvice.com/forums...es-154837.html
Be sure to read the fishless cycling article BEFORE you buy any fish, and feel free to ask ANY questions you may have, in one of the freshwater forums. Someone will be happy to help. And good for you for doing your research before you get your fish.
Have fun, both of you with your new hobby (addicting as you will soon discover).