Mice, rats, whatever.....for a pet feeding mice is A-Ok. Nice thing about rats is that they are quite hearty compared to mice and make much better (cost effective) meals if you have breeding aspirations. That said, even a "mouser" that feeds consistently will put on enough weight to breed in most cases. You'll just have to feed multiple mice.

1 or 2 mice every 7 days is certainly not under-feeding. You may not be getting them to their maximum weight possible in a given time frame, but you are certainly not starving them by any stretch...