Second
DJ's recommendation - KOWD is good for Boston (as is Hanscom Field: KBED).
Start with KOWD then move to KPYM, KHYA (has rental cars & is mid-cape).
If you're adventuresome try Falmouth Airpark (5B6) and call Enterprise for a car (but a bit pricey this time of year!).
KPVC & KCQX are good, but transportation is always an issue. (Tim @ KCQX has a car he might make available, but only for limited times).
Good accommodations near KHYA & KOWD.