How about just running 110V to the pit spaces and then using individual power supplies? I guess I'd be a little paranoid running all my chargers from 1 power supply. What happens if that supply takes a crap on you? Now all 3 of you are out of luck.

I'm in the process of wiring up my 20' enclosed trailer for the same purpose but I'm just going to run 110v to each of the 5 pit spaces.