Kill traps are the only humane way to do it. Poison is slow and painful and you run the risk of them dying and rotting behind a skirting board or under the floor. They might also be eaten by a cat or owl so the poison gets into the food chain. So called humane traps mean they may be left in a small space for hours without food or water to starve/dehydrate slowly. That’s before you even get into the frightening experience of being handled by people and transported to a strange place. A kill trap is instant and pain free, it’s not nice to do because they can be very cute but it’s the kindest thing to do if you don’t want to share your space with them.
And as a wise ironmonger said to me many years ago ‘ if you’ve got one mouse, you’ll have two mice and once you’ve got two there’s no end to it’. One female mouse can comfortably give birth to 100 young in a year so you really need to stop that happening1