Many trade offs to consider. Having done a fair amount of Scout camping trips with our Troop, (I was Scoutmaster for several years) I have to agree with the comment earlier about Scout bags being made from a synthetic fill, more for safety and practical reasons. For an adult, I've enjoyed my modern down fill bag. By modern, I mean something with a good water repellent shell, and treated down. I happen to have one from EMS (Eastern Mountain Sports), but there are many good ones out there. The exact model I have isn't made, but the current version is called a Mountain Light 0 degree long.
http://www.ems.com/product/index.jspproductId=12723076&cp=3677338.3705267

The great thing about this type of bag is the warmth, obviously, but it also will come with a compression sack that will cinch down to where it's not much bigger than the size of a Nalgene bottle! You will pay for a bag like this, but if you sleep well, and have a lighter pack, it'll pay dividends for many years.

I usually sleep on a Thermarest Prolite pad. It's very important to have a good pad under your bag.
http://www.cascadedesigns.com/therm-a-rest/mattresses/fast-and-light/prolite-2012/product

More than anything, enjoy these years camping with your boy. As my dad told me when we were standing in the nursery at the hospital when my son was born...

"Find a way to enjoy a little something every day with that youngster, because before you know it, you'll be dropping off suitcases at a dorm room, and wondering where the time went."

He was right, just glad I had the chance to sit around a bunch of campfires with him before that happened!