No matter how you cut it your shore line is going to be a problem. Every site is going to be different, a high school is going to have a regular plug, a park may have a connection box rigged for trailers. It is not just that a outlet is available, but each outlet has to have its own branch circuit, protected by its own breaker. You are going to be playing Russian roulette every time you pull up to a new site, that the outlets available have enough amperage to handle your trailer. You many find right in the middle of your busy sales, you lose power, and the people available have no idea where the main breaker is, or that the wire that is feeding your outdoor outlet is under rated and is over heating and won’t handle your amperage. There are trailers setup for going around to state caravels, and there are trailers that setup at a spot in town and have a building that they plug into for power. If your trying to strive for every situation, go with a generator and be self supporting.
Then the amount of distance comes into play, your going to have to learn how to run wires for different situations and different lengths and recognize a limitation of the distance. Truly the best answer is a good generator that handles all your needs. Pull up fire up the generator and don’t worry about all the electrical. The wattages / amps can be worked out and a regular breaker system can be setup. RJF