Hi,
If possible, on a 30 amp service, draw no more than 24 amps continuous. Over that number, monitor voltage carefully.
I've added two auxiliary shore power cords, one for the converter for when there is a single 15 amp service. I plug in just the converter and use my inverter for the "house loads".
The other auxiliary cord is for my water heater (and an extra plug). I use it in campgrounds where there are 30 and 15 amp outlets.
For "switching" I used regular male and female plugs, so I can move from OEM configuration to auxiliary in about ten seconds.
The same thing could be done when there are two air conditioners. Simply add a plug system near or even right in the power center. If there is no place for a plug then an appropriate switch could be used.