What tree for privacy that isn't huge, south facing garden

I've got an Acer in a pot currently but would like to plant it in the ground near a fence to give a bit of coverage and privacy from the neighbours. Firstly what's the best way to protect it from damage while it's small from kids playing and things? A temporary wire barrier?

Secondly what tree would go well next to it? It's a south facing garden so don't want anything huge that it will block all the evening sun.