Kids are great! They have very few expectations. They are thrilled by the simplest things. Coming up with good simple wholesome money making ideas is easy and can be fun as well. A lot of times what you and I see as a burden children would have fun doing. That is just their nature. For instance, having a bake sale is one of the funnest things to do with your kid.
Stop thinking about the sale part of it. You are thinking like an adult and not a kid. The fun part is in making the cookies and cupcakes. You need to think about what part of a money making idea is fun to a kid. if there are no parts to an idea that could be conceivably fun to a child then you should probably move on to a new idea.
For kids, unlike adults, its the journey that makes something fun.