We will be flying from Manchester SOON!

I'll be able to offer details on the experience mid-May.
We also chose Southwest because of their $89 fares (after they first came out some flights dropped to $79, but they had stops, and the times weren't as ideal for us, and the overall price was similar because of the stops). So, for 4 non-stop flights we paid $783. So that's apprx. $195 return per person (including all taxes). At the time, there were some reasonable prices ($99, $109) from Portland, but they weren't direct, which adds on a few extra $$. If it was just 1 or 2 of us, I would probably have chosen to fly from Portland... but the more people you add, the more $$$$.
There are many park & fly hotel options. The prices are reasonable. We have always done the park & fly with the Hilton Garden Inn at the Halifax Airport and the prices seem comparable to that.
When we were trying to decide which hotel to go with, we came across many positive suggestions from the transportation board regarding the Highlander Inn. I kept looking, and found the Holiday Inn $159.99, the Holiday Inn Express, and the Sheraton $135 +tx (to name a few). [note: those are prices I had scribbled down in my planning binder, I think they are with the CAA discount]
Everyone's needs are different. It was important for us to have a free shuttle, a place that allowed unlimited parking and an indoor pool ('cause I REALLY need the kids to burn off some energy and get a good night's sleep)! Free breakfast is also a nice bonus when you can get it!
Also, regarding the driving distance. We are still a little undecided about how far we will drive. So far, we are planning to leave early am and possible drive to Portland and spend the night there, just so we can do a little bit of shopping at the outlets in Kittery the next morning before heading to Manchester. On the way back, we get in at 5:30pm and are planning on driving that night to bangor and staying at the Super 8. Then we'll get up the next morning and drive the rest of the way home.
Hope that helps a bit, I'll try to post about the to/from experience when we get back!