I'm having similar issues on my 5er. After research, I think my AC is running ok, but it's hard to expect more than about a 15* drop from the outside temp. Maybe you can get 20*. Which is still stupid hot when them outside temp is 115* (I'm in Phx as I type this).
The generator in your RV should be more than adequate to run both AC's. That would be my suggestion. It will certainly help more than running 1 AC. The reflective insulation in the windows will also help.
I'm sure you are already doing this, but run the AC 24 hours a day. It is much easier to cool the inside of the RV if it starts out cool. If you are starting from 100*, it is REALLY hard to get a significant temperature drop.