I hiked to the peak of Mount Chocorua this fall with my children, ages 12 and 7. They both love hiking and were excited for it, so even though it was three hours up and two hours down, they had a blast! The trail was well marked and easy to follow, but it was definitely a workout! The views of the White Mountains from the top were absolutely stupendous, well worth the trip. We took the trail off of the The Kancamagus Highway.
We brought our bathing suits so we could splash around in Champney Falls on the way down. We even found a "natural water slide" down 10 feet of mossy rock landing in a small pool of water. The kids loved it!
You can get trail maps at the Ranger Station at the start of the Highway (off Rt.16 in Conway), or visit: http://www.mountainsummits.com/mountains/newhampshire/chocorua.htm for more info.