I have learned to slow down and manage my expectations.  Hiking to a fixed destination may be worth it for adults, but I have had some of my best kid hikes just rambling around the woods - enjoying the journey (no matter how short).  At around age 2 or 3, my kids loved finding balance-beam logs, climbing small rocks,finding flowers, or bees on flowers, and looking under logs for bugs.  My two year old daughter loves to find ants - we don't get far, because she has a great eyes for finding them, and she gets super excited  We don't always get far, but they love the low-pressure opportunity to explore.  It is great watching their faces beam with pride for accomplishing small feats (stepping over rocks or branches).  We have done longer hikes to destinations with the aide of the carrier backpack, and my now 5-year old son is an avid destination hiker.