Sassy_C, having lived in an old house (no charm, just old), and having tried lots of ideas, my advice is:  get a cat! Or more than one!  I tried traps and kept the little suckers, but more relatives kept coming to the funeral!  At night I could hear them chewing a new hole in the wall after we'd "permanently" closed one.  I was soooo glad to leave that house.  My biggest mistake:  I did not bring cats into the house.  I THOUGHT a cat or two would be too much trouble. Now I know they would have been a blessing.  Personally, I love old houses.  Especially the ones with a huge porch and wonderful woodwork.  The house we had was just an old farmhouse that was basically sitting on the ground (very short footings).  So the mice didn't have much trouble getting in.

Good luck with the house, hope it becomes your HOME...just get a couple of cats! 
the momster

Cats can be great mousers as long as you feed them really well!  The old notion of "barn cats" not being fed regular food so they will eat mice is BALONEY!  They chase and kill mice ONLY when they have enough energy to do so...  In fact, "feral" cats who live their entire lives outdoors without supplemental feeding rarely eat mice -- too hard to catch!  Crickets are easier...

Here is a website a buddy of mine has that has great info on "pests."  http://www.askthebugman.com

This is one question and answer on mice:

Q:
I'm wondering if the ultrasonic noise makers really do repel mice like
the packaging says they do. We have NO idea where the mice are coming in, and we've been looking for their route for years.

Our local exterminator company recommended and used rodenticide boxes.
And, of course, we got the problems you frequently talk about.

My local hardware store sells a couple of different kinds of ultrasonic
devices that supposedly repel mice. They're worth $20 each to me if
they really work and don't harm humans. I'd put one in every electrical
outlet in my house!

A:
Those ultrasonic devices are worthless. The only thing they will repel
is the money from your wallet. The best control is using Repeater or Tin
Cat live traps and catching and releasing the mice. Snap traps are a good
option also as they kill the mice quickly. Rodenticides have no place
in rodent control as the rodent will often die someplace where they can't
be retrieved and cause an odor problem or even a health hazard if the
rodent was diseased. Also the chances of an accidental poisoning are high.
There are numerous cases every year of pets and kids being poisoned by
rodenticides. Glue boards are not only hazardous to use, but they are
barbaric. A trapped rodent will urinate and defecate continuously
while trapped. If it has hantavirus, it will be spreading the disease into
the air through its feces and urine.

Another method that I wouldn't recommend is setting a mouse on fire.
One fellow in New Mexico threw a live mouse into a pile of burning leaves.
Before the mouse died, it ran back into the fellow's house causing it
to burn to the ground. That is kharma.

I lived in house built over 100 years ago.. and believe me.. mice were the LEAST of my problems.

150 years old!!! Wow, I am stressing out about a house that is 30 years old!! Geez...

I think restoring an old house would be so rewarding...though hard work.  How fun! As far as mice, I would agree to definitely get a cat or two and it sounds like you have that covered.  When my family moved to New York back in the day, we lived with my grandparents in their 90 year old house.  The only mice I had ever seen were desert mice so I about had a heart attack when a mouse ran across my feet when I suddenly walked into a room.  Ewwwwww! You always knew when someone had run across one because their shriek would echo throughout the house.  And Sassy you would have died because one winter we found there was a hole in the basement somewhere and rats got in. Yes, huge NY rats were running around our house!  Geez, thinking about it again makes my skin crawl! We would sit in the kitchen for breakfast and hear scratches and noises coming from behind the cabinets...and if we stayed really quiet, you would see noses start to pop out.  Thankfully the rats were taken care of right away and I'm sure if we were allowed to have a cat or two (grandpa & grandma were allergic) it would have taken care of the mice.

Velocity....OMG...yes you are right I would have died! I watched a reality show about NYC health inspectors and rats were the main topic....one women had them fighting over scraps in her kitchen every night....Eeewwww...icky, icky, Ewww. NYC rats are the biggest I've ever seen and that was on TV.... Sick
I am hoping since we are going to be far from the city that there won't be any rats! Otherwise I'm living in the truck til they're gone!
Thanks for the vote of confidence on restoring an old house! I'm sure it will give me many topics to discuss over the next couple of years.....y'all been warned!
We move the the middle of October....I'll know more then and let everyone know what the situation really is like!

Velocity, THAT WAS HILARIOUS!!!!  I could just see your grandpa in the kitchen with a shotgun ready to shoot anything that moves!   

Anyone see Ratatouille? (I'm sure I butchered the spelling!)