Any advantage to series connecting small 12V chargers?
Better chargers reduce the current when the battery is almost full. But when three chargers are connected in series, the reduction of loading current may occur at different time. If one charger operates with reduced current and the others with full current, the chargers or the batteries may be damaged. Without knowing the chargers it can't be predicted what will happen when the chargers are connected in series.

But in my opinion, a real sportsmen would walk the full golf course instead of using a golf cart.