Tumalo Falls is a family-friendly 1 mile roundtrip hike if you head only to the upper viewpoint.
The viewpoint is only footsteps from the parking area, and gives the best view of the 89-foot falls. A half mile trail leads visitors up to the upper viewpoint, right next to the falls. From there, Middle Tumalo Falls is around one and a quarter miles up the trail and Happy Valley is around three miles and a thousand feet up.
Along the way, there are a dozen or so smaller waterfalls and scenic pools. On the way back to the parking area, there is an unmarked (and very unofficial) trail that leads to the base of the falls, affording a chance to hike behind the falls themselves.