There are lots of nature trails for hikers of all experience levels at the Blue Hills. The trails are never crowded but you don't get the sense of being the only one there, either, so it feels safe. There's lots of parking available, making this a great spot for a walk on a beautiful day.
There's a museum nearby with lots of animals for kids to learn about. And the location is right near Route 128, so it's easy to get there.