The important thing with a seperate coffee shop with meals is that you have to make sure that you have the numbers going past the Coffee Shop. Otherwise alot of the food you order will go out of date.
As a guess and I am only guessing you probably wouldn't do a coffee shop with cakes, lunch,dinner and snack menue under 4000 people per week. If you are doing over 8000 people per week it would be alot more feasible. These are my thoughts only does any body else have any other thoughts/ experiences?