We offered lemonade (of course), lemon cupcakes with chocolate frosting, brownies and sugar cookies. We had friends stop by and kids enjoyed receiving "tips" from appreciative customers.
I used the adorable Lemonade Stand kit from Paper & Cake to impress the neighbors. They really seemed to enjoy the straw tags. When the kids handed over the glass of lemonade and they saw the straw tag, the kids got a tip.
I did have them wear $5 aprons that I purchased at Smart n' Final but Chasen took his off :(