Personally, I'd rather go without food than work at a fast food restaurant. It'd be god awful. Try to get cashier jobs in places, or work in bookstores or something pleasant.
I don't think you can just become a cashier anywhere, especially at 14; I don't know where either of you live but here in this part of the US it seems like everywhere has some job below cashiering, like being a stockboy or dishwasher or something.
I wouldn't mind working with food, obvious by the job I just got today actually working at a pizza place, but fast food is just gross imo.