Excel can do stuff like that but it's clumsy. I agree that you should stay away from it. I think a database is a better option. If I were a server/valet, I'd probably do it in FileMaker Pro, unless I wanted an exercise in Programming Cocoa. In FileMaker it's very quick to add new reports, statistics, etc. and put it in a usable interface that isn't clumsy like Excel.
If you have FileMaker or the money to buy it, I recommend it. If you don't want to buy it, then yes, invest the time in doing a Cocoa app over excel. Just keep in mind, it will take more time.
Right now, I am converting a FileMaker database (a shopping list app) to a Cocoa application, just for the Cocoa practice. The Cocoa app will look a lot nicer and polished when it is finished, but it's taking a lot more time and code to do it. I probably won't do it again. I have a few FileMaker based shareware products. In the future, I will continue to use FileMaker for database-oriented applications, and Cocoa for the others.