You could extend this project by saying that the tips are shared with a certain percentage for each restaurant worker. For example the busboys would get one percentage, the maitre de another, and the waiters and waitresses still another percentage too. That's the way they do it at some restaurants.
For my fifth graders though, I'm going to stick with the equal share problem as we start our division/fraction study and learning. I'll assess students' efforts as they work with similar ability math peers. This will give me good information for future lessons.