Hi,
Modern electronic battery chargers normally do not require upgrading. If it is above 45 amps output, you should be fine. There are only a couple of manufactures out there still installing a small 30 amp converter/charger. Most are fine.
The battery capacity will be about 220 amp hours per pair of golf cart batteries, and 45 amp charger can take them from 50% full to full in about 4 hours. If you plan on recharging via generator, then about 2 hours per day is normally more than enough to fill them.
My suggestion is to also get a 100 watt solar panel and a low cost PWM controller. Some wire and aluminum, you can permanently install it on the roof, and keep that battery full all the time.
SunElec.com has 12 volt solar panels for a very reasonable cost.
Fred.