catching mice in the house

Question
Hi Natasha, I'm not sure if you're the right person to ask about this, but I'll give it a shot.
My basement has mice.  I was hoping it would just be one mouse, but I've set a humane trap for 3 nights, and have caught 3 mice.  I'm wondering how many more there will be.
 
After catching them, I've been letting them go in the bushes at the back of my backyard.  Do you think this is far enough away from the house so that they won't come back?  (I heard that mice don't usually go farther than 10 feet from where they live, but I'm not sure if this is true)

Also, they've been living indoors for a long time, and the weather is starting to get colder.  Does it hurt them to take them from the cozy indoors to the outdoors so abruptly?
Do you think it would be better to catch them and keep them in an aquarium together until spring?  Or do you think they're pretty adaptable and will adjust to the outdoors easily?
 
Also, I'm a little worried about catching a mother and leaving her babies to die!  I don't know if I can do anything about that though.
 
I'm just really not sure what to do.  I don't want mice living in (and pooping on and chewing up) all my stuff (as they have been doing), but I also don't want to harm them.  Any advice?

Answer
Dear Leah,

Mice will return to their nests from over a mile away!  They need to be let go far away, in some nice wooded or grassy area.  You may be catching the same mouse...

Although I do keep mice I catch until it is warm enough to let them go, you might find keeping them in an aquarium (if there are a lot of them) will be a lot of work.  I would say mice can be left out safely at down to about 45 degrees.  When you let them go it is nice if you can leave some food and bedding for them as well.  

If you catch a mother mouse, you may be able to see that her nipples are swollen from nursing.  If the nipples are visible at all, she has been nursing.  However, this will be difficult to observe.  It's pretty much a risk you will have to take.  It's wonderful that you are catching them live and letting them go humanely.  It would be nice to gently pick them up from their nests, let them pack their luggage, and put them in little hotel rooms!  I wish.  Much as I love mice, I am well aware of the damage they can do to a home.  You are doing your very best.  

Thank you for being a friend to mice.  

squeaks n giggles,

Natasha