This lemonade activity is fun, engaging, and involves multiple mathematical concepts! It covers: scale factor, increasing or decreasing recipes, ratios, tips, tax, commission, group skills, social skills, problem solving and reasoning, connecting math to the real world. You can also bring in lemonade for the kiddos to try. I would have the students work in groups of about 3, maybe 4, and try to convince you to buy their lemonade when they're done while using numbers and evidence from the activity.
I included an outline of what I did during this lesson, the task card, and a rubric I used to grade the finished product.