GettingOldWithoutStyle
others have given great ideas but if it has to be Lego (no judgement! Lego is the only brand loyalty my house has) then you could look at Lego Chima which is no longer made but can still be bought easily second hand. There is a green tank-like one in the collection (chima is warring animal tribes - the different animals have different weapons/vehicles, some really clever builds & very interactive. DS loves them)
Avoid if you only want new as the prices are eye watering!