Your choices are rather limited if you want to play 1v1 against your nephew. TvT and PE are the only 2 I can think of that fit the bill. If you don't mind lots of other players in the game, then WW2OL and WOT are worth a look. If you don't mind modern, then SB is the best. I have not played M4 tank platoon, so I can not say how it plays. It has no eye candy, so it gets crushed by the public.
TPA who TWI