This is NOT a good idea. Go ahead and empty out the innards through the hole, but DO NOT toss them into the run for your chickens to eat. It won't be long until you stop finding eggs to do this with, because your biddies will open all of the fresh ones looking for treats!
That said, though, the method of emptying out the shells is GREAT! I didn't know about the water trick. That's cool!
Instead of giving the shells to your birds, though, try this on for size ...
Go ahead and make that hole a bit larger, stash them in a cardboard egg carton, add a little potting soil or seed starting medium, and stash them in a cool place until it's time to start your seeds in the Spring. Just tear off the top of the carton, and put the whole thing in the garden, covering it with enough soil to go over the carton sides. Your seedlings are automatically two inches apart - perfect for thinning, later on. Or you can carefully cut them apart and plant each one individually. The cardboard holds water. The shell provides nutrients ... and it's all biodegradable.