Begin driving the Going-to-the-Sun Road and follow the signs to Apgar Village and head to the shore of Lake McDonald. Stop at Lake McDonald Lodge and then hike Trail of the Cedars and Avalanche Lake Trail.
Trail of the Cedars is a popular loop trail located 5 miles east of Lake Mc Donald Lodge. Round trip length is 0.9 miles and it takes about 45 minutes. It's an easy, flat hike with plenty of scenery and shade.
You’ll soon reach Logan Pass, which is the highest elevation on Going-to-the-Sun Road. Then hike Hidden Lake Overlook, followed by St. Mary Lake boat tour and Baring Falls hike.
Most visitors walk at least the beginning portion of this moderately difficult raised wooden boardwalk trail, but you’re missing out by not hiking the 2.7 miles (round trip) to Hidden Lake.
I recommend customizing Day 3 to your family's needs. If you’re up to seeing more of the park head to the Many Glacier area, or perhaps you’d like to add in some adventure via horseback rides or a rafting trip.
There can be big temperature changes when going from lower to higher elevations so be sure to pack layers. Gas is not available anywhere on the Going to the Sun Road so be sure to fill up ahead of time.