Honda & Yamaha are the gold standard for inverter generators.
There are some decent lower cost generators and there are some pieces of junk.
The inverter generators create DC power and use an inverter to convert it to AC. As long as the brand matches up the quality ones can sync the inverters to match the Hz.
The biggest question is where will they be camping? Most RV parks have power pedestals, even if they don't, there are usually limits on when you can run the generator making air/con impractical. It's really only if you boondock in remote areas where you can frequently use the generator for air/con.
