Logan's not actually all that hard to get to, and parking is $22 per day in the terminal-adjacent garages, and $16 per day in the economy lots.
If you'll be gone for fewer than eleven days, it'll be cheaper (even with gas prices) to just drive to Logan and park in the garage - and this calculation doesn't even take into account the 'optional' tip to a shuttle/town car driver. And if you opt for economy (have the driver drop everyone and all your luggage off at the terminal, then only that person, unencumbered by suitcases, needs to take the free shuttle back to your terminal), you can park for fifteen days and still save money.