If you're looking for a NATURE experience in the North Conway area, I highly recommend Echo Lake State Park. There's a lake with a swimming area, trails, trees, picnic tables and scenic views. We're somewhat city folk and this was a very doable outing for us, very relaxed and not taxing. The park does charge an entrance fee ($4 for adults, $2 for kids ages 6-11, under 6 is free) which is almost nothing when compared to the cost of other attractions in the area.
This would have been the perfect place to park ourselves on a warm, sunny afternoon which was the original plan. Instead, because of schedule changes, we stopped here for a few hours on our way out of town. Unfortunately, it was overcast with the threat of rain, and while warmish, it wasn't exactly "swimming" weather but we enjoyed ourselves and kids will swim no matter what the weather is.
There were tons of these tiny frogs hiding out away from the beach area. I've never seen so many frogs in one spot in my life.
(This photo is a crop of the one above. I LOVE that 50mm lens. Look at that detail!)
(Those are tadpoles. Millions of 'em!)