Most alliums transplant quite easily. You probably have enough seedlings that you can try it with quite a few and they won't be missed; so you should have enough to play around with. When successful, don't let the extras at the original site mature or you may well have them there and around that place as volunteers for a long time.

If in well drained soil, quite a few alliums can escape and become invasive.

I am quite happy to have volunteer alliums - especially if they turn out to be the huge ones! However, the mass of seedlings is in very poor soil under the cedars so I doubt if any left will come to anything.