If these seeds are from different species that you can't sort out, my advice would be to plant them in a large box and leave them outside : I think (tell me if I'm mistaken) that Idaho has harsh winters. Periods of frost and warmer weather will be as efficient outside as putting them in moist sand in a fridge.
So i'd say put them in a polythene box (the kind of box they sell fish) filled with coarse grit at the bottom, then a layer of fine sand in which you put the seeds, 1cm (half an inch) coarse grit on top, and outside.
I even had a few seeds growing after the second year doing that with a bag of "bonsai seeds"
so if that doesn't work, keep watering the box until the 2nd spring...
One of the seedlings (about 4-5 years, june 2007):
...and after drastic pruning (July 2007):
I know that some of you may be skeptical, but "rendez-vous" in a couple of years...
