We were there a year or so ago. Wow, its really hard to follow the trail, lots of walking, back tracking, up and down hills. Be aware the street and side walks are not in good repair, cobble stones and such Wear, really good shoes for safety reason. At times you will be right next to the traffic, and also there are homes with basement apts, and no railing or warning just stairs going down one of the guys on our trip fell down about 8 steps, he was trying to get a picture and down he went. The line you are suppose to follow will stop for no reason and it might pick up across the street or down the block. Check to see if there is a cost with the stops you might want to see.
The Kennedy Library was the highlight of our trip, well worth the cost, and the university is so beautiful. Check out the North End for Food, great little places to duct into and grab some wonderful really food and wine, and Mike's Bakery is another stop.