Well i never worked in a coffe shop but when I worked in a dry cleaners I was part time, for my lunch breaks I had to punch out so I was off the clock, I got anywhere from 30 mintues to an hour for lunch. Mostly my lucnch breaks were on the weekends since I was in school during the week and only worked 3 to 6. However on Saturdays if I started work at 8 I would get an hour lunch, if I started work at 9 I would get 30 minutes. It all depended on when I started and if I had a full 8 hour day.
Hope that helps
"The Fair Labor Standards Act (FLSA) does not define full-time employment or part-time employment. This is a matter generally to be determined by the employer. Whether an employee is considered full-time or part-time does not change the application of the FLSA, nor does it affect application of the Service Contract Act or Davis-Bacon and Related Acts wage and fringe benefit requirements."
So basically you have to treat them in the same regard. Hence forth, this also dictates that you decide what part-time and full-time means. So 30, 32, or what ever can be the start of full-time.