Another option is to drive to Portsmouth and take C&J, another bus line like Logan Express that has direct service to Logan. My BIL is a flight attendant for United, lives in southern Maine, and takes C&J all the time. I'd probably do this rather than drive to Woburn- the traffic on 93 can be a nightmare, depending on the time of day! With both these services, you want to check and see what time their last bus runs...you'd hate to be stuck in Boston if your return flight is late! With C&J, you go outside the terminal at Logan and look for their bus. You should probably check both C&J and Logan Express schedules before deciding...I think both have websites.
We flew SW out of MHT in June and it was OK, although I prefer to park at the airport than in one of the local hotels (the nearest to the airport charges by the day, not the 24 hour period, so you end up paying for an extra day). Also, unless it's been changed since June, it's not that easy to get a boarding pass on=line. In June, you could only do that for a single party; if there was more than one person on the itinerary, forget it. SW will "break up" your itinerary into separate reservations but they won't let kids "fly alone", so if there are kids involved, on-line boarding passes won't work either. Leaving MHT wasn't a problem; we arrived ~1hour before our flight an got "B" passes, but we queued up immediately so we were at the front of the "B" line and the 3 of us were seated together. However, leaving out of MCO was a disaster! We were at the airport 2.25 hours ahead of time and the line for check-in was enormous! We barely made our flight, literally running thru the airport, and DD (10) ended up sitting in a row with strangers. After take off people moved around so DD could sit with me, but upon boarding SW stuck her in the 1st available seat so that they could depart on-time. It was OK, but what if she'd been 5 instead of 10?