Cheap route is 8x8 timbers.
Granite curbing is the way to go IMO. May cost more upfront but they last forever and look really nice.
I have part of my driveway lined with granite "cobbles" and they stay in place with no problems (I snowblow which is not even an issue for you).
Some of these comments above just reinforce why a plow will never touch my driveway. One errant pass into my elite Kentucky Bluegrass lawn and somebody would have hell to pay
