They won't be back. After they start flying and have returned through the door a few times, make them enter through the bobs. Pigeons can be trapped around some city buildings, bridges, grain elevators and farmers' livestock pens. But it's possible they might be carrying disease. If you're serious about keeping training birds long term, inquire about breeders of fancy pigeons in your area.
Culls are usually available.
You'll enjoy watching their fast-spinning backward aerial somersaults. Raising your own pigeons is easier than most people, including many dog men, think. We disturb them too much. Actually, the solution is simple. Hens hug the floor, twitch their wings and coo, if impressed by the male's performance.