BCT is good from Ward Reservation through HP. OK 114 to Sharpners. The next off road section along Sharpners not sure. Bald Hill ok but there may be more interesting routes through there. The blazed route from Middleton Rd. though Boxford Center to 97 is interesting. Boxford store a welcome resupply, may not be open on Sunday. If you don't want to do Georgetown-Rowley, you can cross I-95 on 97, immediate left on Rowley Rd., look right for singletrack in Cleaveland (alternate BCT blazes, shown on BCT map 2). The rest is good to Willowdale and worth doing IMO.
Have done this several times but with a shuttle. Usually in the fall, bugs can be nasty during the warmer months.