Thank you for the responses. I was looking, instead, at doing concrete curbing but can't find anyone to do it. We only need about 30ft done and don't have a tree in the front to bring the square footage up a bit. No one I've found is close enough that they'd do it for their regular price for that size of job - they all want to throw a $300 minimum in there, which isn't worth it.
So, going back to the rip rap idea...
When using the trimmer, whether plastic or metal, are you talking about leaving it sticking out like it's normally done when people use only the edging for their beds? I think that'd look pretty tacky in front of the stone, obviously. How deep can I put it in the ground before worrying about the grass just going over it (or, better, what's the smallest amount I can have out of the ground)?