Why do you have to preheat everything at your commisary?
Can’t you just transport food at proper cold temp. to your site,then fire up your cart?
I have been inspected before ten minutes after set-up.Obviously nothing was up to proper temperature yet.The inspector noted current temps. and also noted I was not open yet[umbrella not up yet].No problem.
p.s. don’t tow cart while lit!If the flame does go out you are then leaking gas and towing a bomb.