The Snowbowl area offers great hikes, sitting and picnic areas, and scenery for photography during the off season (i.e. when there is no snow.) The trail to Humphrey's Peak (Arizona's highest peak) begins at the base of the Snowbowl and ascends up to 12, 633ft.
Downtown Flagstaff is a collage of storefronts for a great way to spend several hours. Think beer, clothing, treats, food, galleries, and vintage shops.
We'd recommend looking into various hikes around Flagstaff. Alltrails can help you to narrow your search by difficulty, terrain, time, etc.
One of the "Seven Natural Wonders of the World," the Grand Canyon is an excellent stop during the wedding weekend. The South Rim Visitor's Center is about 80 miles north of Flagstaff.