Over Thanksgiving, I'll be "boondocking" in a family driveway. I can plug in to their house power at 15 amps, but that will not be enough to power everything we need at certain times. Can I power up...
Most often the generator will take priority over the shore power. This involves a transfer switch that will prevent a back feed into the shore power. However, to be safe and not try to outguess how your coach is setup, unplug from shore power first and then start generator as 2oldman suggested. The shore power will help with your battery charging and run a few lights and such but not anything that demands a lot of power.