Cracked corn won't kill them, but it is more risky. It can scratch the insides and make it easier for canker to set up. And mold/bacteria has an easier time growing and hiding in cracked corn than whole corn. So if you're going to add something to it, then pellets, wild bird seed, small whole corn, or any other mixes like that will work. Whenever we can't afford to make the trip to get pigeon feed, then we get Gamecock feed from the feedstore in town.
What kind of feeders do you use for them? If you use an open dish, then they like to get in there and pick through their food, slinging out pieces they like less. Using something like this will prevent them from wasting as much, which'll save you money.
http://www.pigeonsuppliesplus.com/photo2.html
Also, taking out the feeder at night will prevent rats/mice from being attracted to the food and contaminating the loft and eating the feed.
About the pellets and gamebird feed making smelly droppings. That's because it has a lot of protien in it. The messiness is probably from all the excess supplements. The pellets are designed to have everything they need in it, so if you give them any additional supplements in the water, or even grit, then it can make the droppings more messy. But since you'll be mixing it with seeds and grain, grit is a must. An all-pellet diet would be different.
