Lisa,
Since packing space is very limited, might I suggest you both pack a Smartwool merino longsleeve crewneck pullover, and perhaps a merino tank or t-shirt as well? They are very lightweight and thin, yet will keep you pretty warm. They wick off sweat, and best of all- they don't smell funky under the arms after wearing them once or twice like polyester stuff does. They roll up really small. And one heavier weight merino zip-turtleneck top would probably come in handy too.
Merino has the ability to regulate your temp- they keep you warm if it's cold, and yet they breathe wonderfully and dry out quickly. Smartwool also makes a great little helmet liner, and also lightweight merino glove liners. And their socks are reknowned of course. They resist getting stinky too. (important when you are trying to pack only a few clothes and want to wear items more than once)
Hoodies are another good choice, since you can pull up the hood under your helmet when your head or neck gets chilly.
You will definitely need a windbreaker/rain jacket that can roll up small. If you have some good merino base layers, your windbreaker/rain jacket doesn't have to be heavy. You might get by with shorts, but you'd be wise to take warm tights or knickers too, for cold days. You should take both fingerless and warm full finger gloves- if it's 40 degrees, your fingers are going to get cold in the wind. Keep checking the forecast for that area ahead of time.

In addition to Smartwool brand, Ibex.com sells equally good quality merino base layers, jackets, wool tights, and knickers, etc.

Sounds wonderful!! We plan to do a few mini-tours in MA this summer, but not camping out on the cold ground.