Yes you are exceeding the rule of thumb, however you are so close in my mind it does not justify spending more money.
If however you were running a
continuous load at a full 12 amps or more than #10 would be prudent.
Sounds like 100' is what you are shooting for? Bet you are running several small loads and maybe a refer. You want the generator about 100' away for noise, lets say.
I would run a nice fat #10 cord that I made myself with a WP plug into the gen-set and hard wired into a 4plex box, probably weather proof, and then some cheap #16-25' cords from there.
Or move the generator to 75' and use #12.
