When I would take my oldest son with me usually what I did was make our meals separately - so that each person could choose what they wanted, at any given time. And no need to break it out after cooking. Anyhow, 2 bags will still fit in one cozy though nicely.
As for pot size? It depends. I usually carry close to a 2 L pot if there are 2 of us - but that is because I like drinking hot drinks quite a bit. So when I boil water, I do 4 cups for dinner, and 3 for drinks, plus a cup for washing up faces and hands or so. :-)