sounds like you've patterned the coyote, you know he's coming at dusk, you've got the "bait" your springer in a cage, what is a "mongo"?
maybe chain him close to the house or the springer(s) and be ready with tour gun. I bet posting an invite at the local sporting goods store would provide some willing volunteers as well. maybe have them set up in the woods where you think the rest of the pack is waiting; this should be easy to find the morning after.