This isn't the only brand, but you can read about granular castor oil pellets at this site. It doesn't kill moles and other rodents, but does repel them by the smell. It won't hurt you, your kids or your pets either.

Here is a link that might be useful: mole repellant

sounds like a vole problem

Most likely voles. They are very destructive in some areas. They can be controlled and damage minimized with bait stations and specific cultural practices...it will be an ongoing battle:

A Bait Station for Voles

Easy Bait Stations

Voles -- "Be As Inhospitable As Possible"

If you know someone who is a member of the American Hosta Society, see if you can borrow the last issue of The Hosta Journal. It has a very detailed article on building bait stations.

I have had good luck coping with voles by making chicken wire baskets that I place in my planting hole, and then planting in that. Basket seems to protect enough of the root mass that the plants survive...or perhaps the voles find biting on chicken wire like chewing on aluminum foil?

Regardless...it works!