Since you and your 8 year old are total beginners, may I suggest that you start out playing the Capture Game? You can play on a small board like the 9x9, but I have a friend who enjoyed the 7x7, and it's a faster game on that board.
The object of the capture game is to capture a stone. OC, you still win if you capture more than one stone.
You also win if your opponent does not have a legal play. For instance,Suicide is not allowed, and anywhere Black plays would leave that stone without a liberty, so Black has no legal play, and loses.
Capture games are quick, so you and your son can play a lot of games.
They are also strategic, at least on 7x7 and larger boards. You can also play Capture 2, Capture 3, Capture 4, and so on. The more stones you have to capture to win, the more the game is like regular go. You also quickly get the idea of which stones are dead or not, a question that beginners often have. The life and death of stones is very important, and there are many problems with that theme.
When you start playing regular go, you may enjoy the 9x9 board. The games are relatively quick, and the 9x9 is not a baby board. Even pros sometimes play each other on the 9x9.
The 19x19 is great, OC, and the scope for different strategies is enormous. But, as always, life and death are very important, and most of what you learn on the 9x9 transfers well.
Welcome to the world of go!
Bonne chance!
