Thanks for the input guys. I ended up using a hammer to break a couple of them out of their shells (it was very easy) and toss them into the tank with the baby bimac. The bimac has only eaten live food up to this point, so I don't want to kill them in the freezer. I suppose I could anesthetize them by chilling them for a few minutes first, but I think the tank water would warm and wake them up anyway, just in time to experience the thrill of being eaten alive by a monster five times their size, so I decided it wasn't worth the trouble to chill them.
What should I feed the hermit crabs waiting on death-row? I figure a little flake food should do it for them, but if anyone with experience has any better ideas, please let me know.
Oh, and just to add to the public knowledge-pool:
I collected a bunch of little clams at low tide that are about 1/2" long. The baby bimac ignores them if they are closed, and even if I open them, he rarely eats them. I wasn't comfortable relying solely on them to keep him alive. Even though the clams and the bimac both live in the local intertidal zone, the clams live in the flat wet sand, while the bimac lives in the rocks/tide pools, so a baby bimac probably never sees one of these clams.
I expect the live, deshelled, hermit crabs will solve my problem, but I won't be able to confirm that until tonight (I left for work right after I tossed them into his tank this morning)
Thanks again for all your help