I would suggest offering a discount to any group of three or more so they get in on the 'me too' principle.
People like to do things if their friends or neighbors are doing it. I built my initial business on the 'me too' principle. I used to go down the block knocking on all the neighborhood doors, until I had convinced one to have their lawn done. The first job would sometimes take 20 doors to knock on before one would give me the go ahead. Then every second door it seemed would give me the go ahead once they heard the machine running and saw that their neighbor was having it done. In fact several times the people that I had asked earlier on in the block who had said 'no thanks' to me at first would search me out down the block to tell me that they had changed their minds and would like to have theirs done as well. No one wants to be first but everyone wants to be included once someone has started the process. I learned this early in life through these experiences. Even if I didn't have a first customer yet on the block I would start the engine and have it idling as I would knock on the door and say "Hi I'm aerating your neighbors lawn down the block today, would you like yours done as well? I could do yours right after I finish theirs and you would qualify for the' in the neighborhood discount'." Most people would go with the plan because they wanted to save money and have what their neighbors were having. I was only 16 when I was doing this approach and I later discovered that this same marketing and sales approach is used by major sales corporations. This exact wording is effective still today, 20 years later, for direct selling of aerating services.