Even my well-grounded children have a harder time not wanting little goodies when we are visiting a location that they won't likely return to soon. Plus, they want to hold onto that memory and are afraid that when they leave, that it will all be gone. Having some spending money is a great way to handle the desires and to teach them to budget. Having a lemonade sale teaches them about the value of money because they had to earn that spending money. It gives them ownership of their funds and a great since of pride in having earned their spending money.
We live a bit out of the way of traffic to have a lemonade sale typically. However, last summer, we were having a garage sale with friends in a more urban environment which offered enough traffic for an old fashioned lemonade stand. We were going on a big family road trip to The Grand Canyon, Washington State (husband's family lives there) and Yellowstone National Park. We knew the kids would want things here and there so having money they earned would alleviate trying to decide how to make souvenir shopping less painful and expensive.
What we used:
Large batch of lemonade (put it in something with a spout or it will get dumped out inevitably)
Fresh baked cookies (because they smell good and make you thirsty)
A chair for each child
A money jar
Small paper cups
Napkins (for the cookies)
A sign to help promote
I left them to it and my daughter was quite the sales lady. She really wanted to have money to spend. She was pushing major cookies and lemonade that weekend. They rotated shifts in the end, but that was left to their management.
In the end I divided up the money (added a little proceeds from the garage sale to make it even) and put it in an envelope for each child. They did pretty well too. The best result though was what I saw when we went on our trip. They were selective, careful, and made fantastic choices. When it was their own money, they were much more willing to wait for what they really wanted. They loved showing of their hard earned purchases with pride too!