I know my response is late for your Rothbury experience, because Rothbury has already happened, but I use an inverter and my car battery all the time. It's the perfect solution for me because I never run out of juice that way (take jumper cables though, just in case).
Unless your truck's head's need replacement and you're spitting out black clouds from your trucks exhaust, I DEFINITELY wouldn't worry about that. Shit, when your neighbors are probably gonna be partying at 4am, shooting fireworks off in the middle of the night, playing their music at 6am in the morning, pounding their djembe drums until the wee hours, or generally being up shooting the shit and making noise...bottom line is that you shouldn't need to worry about running your truck once a day for a half hour in order to keep your truck battery charged up. I often sit in my car during a hot festie anyways just to get a mid-day blast of A/C!