It's important to limit activity, hiding toys is a good idea, encourage laying down for a petting. It doesn't help to tell a puppy "take it easy, you just had surgery!" and it's not easy to keep them mellow - good luck!

By the way, my dog took a 3 foot jump the day or so after her surgery. She let out a yelp but was fine - so don't worry too much if they overexert themselves by accident unless the pain continues for more than a yelp.