It's a great idea I think she'll love it.
I was proposed to while finding a fake geocache and I loved every minute of it.
Foodee set up a nice long night cache and left the ring in the final. I made the find and realized that the little black box was for me (by the way the realization took a little while), I then called him a few choice words (for leaving the ring in the cache) before saying yes. I think I got him a little worried there...
It was perfect though I couldn't have been more surprised.
Good luck to you.
