The wedding ceremony doesn't start until 3pm (Mountain Standard Time) on Saturday (with some getting ready time needed beforehand, of course!).
Therefore you will have time to spare on Saturday prior to the wedding, and Sunday following the farewell brunch to explore the area.
Here is a list of small hikes and sites to see in Rogers Pass. Also make sure to chat with the staff at Heather Mountain Lodge for other tips - they are experts on the area!