Insulation...what kind?

[TooManyTails]

I live in central New York, or winter temps at night usually hover at about 15-25, sometimes lower. After a few conversations with the husband, we've decided to seal up all the cracks along the walls, door and window to prevent drafts, then tack up some foam board on the ceiling. Both front and back tops of the walls are vents, 4inches tall by 2 1/2 feet long (3 each side), the back wall is 6 feet tall and the front wall is 8 feet tall so in really wind times we'll close up the back side vents so the moisture can still get out the front higher vent. Im gonna pick up 2 thermometers (one for inside and one for out), maybe if i can get one that measures humidity for inside and I'll just monitor that way. Not failing to mention just watching the girls and how they are acting!!!! Does that sound reasonable? I know I can be a bit over concerned!!!! And everyone input helps sooooo much!!!