I'll throw out there that Deuter makes a good women's pack that has lots of adjustment and is eminently comfortable . Something in the 60-65 liter range will do you for what you want, as long as your sleeping bags aren't cheap monstrosities that have very little compression. Other than that, pads can lash outside or go inside, depending on what you bring. Down bags will be very compressible and light for the warmth they provide, look for used or deals. I wore wool pants, fleece vest and a fleece jacket that cost me 18 dollars total at a thrift store and they kept me warm on a trip that dropped to zero this past weekend.
As long as you keep your sleeping bag bulk down, and your tent size not too large, the pack size you specified will easily fill the bill. Maybe more important than any advice I can throw your way, a heartfelt prayer said for your son and your whole family. I hope all of you have many, many happy miles on trails together.