I would never want to own mice, with all the stories of how they smell.
But gerbils... no smell at all
We like them as pets too. As long as they don't have names it's easy enough to designate them as snake food. I can't see a garter snake ever eating adult rodents anyway. Much too big. When an older gerbil (with a name, of course) dies, we treat it as any other deceased pet.
Even if you didn't like them as pets, would still imagine they'd be a less smelly choice of feeder animal, albeit with smaller litters and bigger cages required.