Nickerson State Park in Brewster for biking, hiking, fishing. Old Jailhouse in Orleans for dinner -- Brewster Coffee House for breakfast.
National Seashore for outdoors and beach activities -- Old Kings Highway in Brewster, Orleans, Dennis, and Barnstable for historic homes. Heritage Gardens in Sandwich (Beginning of the Cape - on Rte 6A) for gardens, flowers, history.
Take in a CCBL baseball game in Orleans, Chatham, Brewster (and other Cape towns) -- All-star college exhibition players -- best college baseball you'll ever see = cost $2 ... runs every night for ten weeks.
Academy of Performing Arts for plays - very good local live theater ...