So, I'm trying to gear up so that when the opportunity for a 2 or 3 day backpacking trip comes we'll have what we need, but of course divorce + new job + preparing to buy a house = cash shortage.
I have a 14yr girl, 13 boy & 10 boy.

For a backpack this was tempting
http://www.walmart.com/catalog/product.do?product_id=3905445

but I decided external frame backpacks would probably last longer, so we tried these on at a big box where they were $114
http://www.campmor.com/webapp/wcs/stores...;productId=9084

on the two biggest and they look like they'll adjust just fine for 3 or 4 years, so I bought 2 from campmor. I haven't figured out what to do for my youngest & smallest yet.

We have big, heavy, rectangular cotton bags that have been used for fair weather car camping & sleepovers, but now we need light backpackable bags.
I've tried to search out everything I can about down vs man made fibers but am still unsure. I want full size bags so that they can be used all the way to adult size, which the 14yr old girl is 5' 6" already & 13 yr old boy is close to that. I expect mostly milder, 3 season camping, but 2 of the kids sleep cold.

This is tempting, but I think it'd be to cold & not last
http://www.walmart.com/catalog/product.do?product_id=2579726

Then I think this
http://www.campmor.com/webapp/wcs/stores...mberId=12500226

Then I think wet conditions with kids would demand this
http://www.campmor.com/webapp/wcs/stores...mberId=12500226

I don't want to be to cheap but for me $120 per bag * 4 bags is my credit cards limit.

Suggestions?