I would strongly recommend NOT using any military style bag. In any place that you or your family would use the system of your choice it would be best NOT to look like military. I have read a lot of posts that people are telling others military clothing, packs, gear, and rifles or the best thing to use. They are not!
To your question you can not chose a pack from looks alone it should be able to hold the things you need but be able to to carry. Most people load their packs with so much they cant carry more then 100 feet so the pack should be picked according to the person carrying it.
I use the Blackhawk assault III Day 134.00.
It is black 2000 cu. In. Very nice mine has held up through Everything I put it through.