I would actually venture to say that mice are meaner then rats. There should be no risk of injury to your animal as long as you supervise feedings and don't leave a live rodent in there unattended. That is when the accidents happen.
If you still want to stick with mice then you will end up feeding multiple mice per feeding about once a week. If you do end up feeding multiple mice in one sitting, don't throw them all in at once. Wait for the snake to eat the first one and realign its jaws and then offer the second.