Well, first and foremost, listen to your vet's instructions regarding limitation on activity. You may have to take a break from training for a day or two post-surgery to give any swelling and pain time to subside. Other things should be kept to low impact activities. Working on sit and down stay could be something. Touch games where the dog touches his nose to your hand. To give him something to challenge his brain, try something like a shell game and hide cookies under some cups and let him find it.
The most important thing, though, is to keep your vet's advise in mind because you don't want to pop stiches.