Generally, exploring and discovery is enough for kids, but sometimes even they can grow bored with that and become restless. Remember that they naturally have shorter attention spans than adults.
Fortunately, there are lots of tried and true activities you can do on the trail that’ll keep kids from getting bored. Among them is "Indentifying Animals. "
Bring a kid-friendly field guide and see how many animals you can identify on the trail. Most of the animals you see will be birds and insects, though if in the Southwest, lizards also will be in abundance. This also is best for older kids.
Materials: Field guide.
Ages: 10 and up.
Read more about day hiking with children in my guidebook Hikes with Tykes.