Big lead acid batteries are the best power source there is for a charger, if you don't mind lugging the heavy beasts around and maintaining them. Cleaner power, no hum or ripple, they don't care if someone else trips a circuit breaker, etc.

Running 2 in series for 24V is easier on the charger and batteries, a little less heat for the charger, and less discharge on the batteries, as lead acids don't like a lot of discharge. Deep cycle marine types would be even better. The 2 in parallel for 12V would also reduce discharge of each.

I don't have much to add on the charger choice that I haven't already rambled on about. They all will work fine.