I don’t know how well this will work for more than one dog, but searching for stuff has worked very well for me. Using their sense of smell makes them expend a lot of energy.
Initially, the “stuff” will be treats, of course, but that’s the part where it might be tricky for two or more dogs. You don’t want them to fight for the treat.
Maybe take turns at first?
Anyway, you let your dog have a sniff of the treat and then tell your dog to stay (close a door if they don’t know how to stay very well) and go hide a treat. Come back and tell him to search. If he doesn’t understand at first, call him towards the hiding place. He’ll catch on quickly.
The goal is to make them smell, and not just search with their eyes. This might take a few tries or maybe a couple of weeks. Keep trying creative hiding spots so that they’re easily reachable but not easily spotted (visually).
You might find that they’ll try to follow your scent (where you’ve been) instead of the scent of the treat. That’s good initially, but later you might want to try walking around elsewhere to throw them off.
As they progress, give them something else to sniff and hide. Follow him close as he searches and as soon as he finds the object, give him the treat. I suppose that at this point, you can have both dogs searching at the same time and treat them both regardless of which one found it.
The final step of this hide-and-seek game is to have them “signal” you when they find it. I believe the most common way is just to sit close to the thing you hid and look at you.
As you can see, I laid down several steps. Each adds more mental stimulation to the game, which is also rewarding to dogs.
