[JRTJH]

The generator appears to be a "off brand knock-off" obtained from a mail order business. I'm not suggesting that the generator is not worth the price paid, rather that many "low cost, off brand" generators are either "rebranded rejects" or "remanufactured and rebranded, low cost sales items"....

You didn't indicate that there's any problem when the trailer is connected to shore power, so if it's working on shore power, then the 30 amp RV main breaker is carrying the correct load and the A/C is working. That means the trailer is probably working normally (or the 30 amp trailer breaker would open with the A/C load). Assuming that it works on shore power, I'd suspect it's a generator issue.

Before spending a lot of time on trying to troubleshoot the trailer for possible problems, it looks like this is your son's generator and the problems are with the generator, when connected to his trailer....

Why not connect his generator to YOUR trailer, see if you can replicate an approximate "amp draw" by turning on ONE of your air conditioners. If the breaker on the generator does the same with YOUR trailer, I'd suspect the generator first and not the trailer. If, however, the generator performs well in powering YOUR trailer, then I'd suspect that your son may have an issue with his air conditioner and/or his trailer....

I'd suggest you verify that it's the generator or his trailer by connecting to YOUR trailer to see if the generator is performing to specifications. That way, you'll know where to focus your efforts rather than "blaming both and trying to find out which one".....