White Pass to Chinook Pass. Just shy of 30 miles. Scenic, scenic and more scenic. The first half is on the plateau full of lakes then cross Bumping River (a tiny stream) and then hike up to alpine splendor and more lakes with gorgeous views of Rainier.
You really cannot go wrong with this section: it is easy, the elevation gains are easy, the trail is well kept due to the horse groups in the first half, the "ford" of Bumping is something a 4 year old can do....and you don't need any pesky permits except for the free one at the TH. That and the two parking lots are not far away for 2 cars. And...you can make it into a semi loop as well!

Just go later to avoid bugs though <img src="/forums/images/graemlins/frown.gif" alt="" />