Ok to run a generator at night if no one is around?

Look at the diffusion coefficients of gases ( in most any chemistry book) and you'll see that it would be virtually impossible to get a high enough CO concentration in open air to create any health hazard. Built in gennies exhaust along the side or under the vehicles or trailer and its no problem. A bigger concern would be overheating the extension cable unless it's 10 or 12 gauge.