Rob B. on Great Blue Hill Trail
A solid day hike that's moderately strenuous for adults and strenuous for kids. The trail is very dry and gritty (in late August). Small rocks (almost gravel) make some of the steeper portions a bit treacherous as they're prone to slide out from underfoot.
Eliot Tower is a great destination for lunch; there are several picnic tables available and it's a logical place to take an hour and let your feet rest before continuing down. Parking is ample off Hillside Street, but take note that the parking lots tend to fill up in the second half of the day (a lot of folks coming to the beach at the pond there). The view from the top floor of the tower is quite good; you can see the Boston city skyline and even some of the boats in the harbor. It's worth it to pack a small set of binoculars to get closer to the action.
The view from the rest of the trail is somewhat underwhelming if you've hiked other New England trails; remember that they're Blue Hills, not White Mountains, and set your expectations accordingly.
No bathrooms once you're on the trail, so make sure you use one of the restrooms at the parking lots.