You have seen the blue duffle bags on our bikes numerous times in the pictures. The bag is made by Seattle Sports and is waterproof. The thinking, again gained by online research, is to have all the items that go inside the tent and need to stay dry in a separate waterproof bag that can be put inside the tent once it is pitched.
This system worked out really well not only for camping but also when we had to stay in hotels since we took it and our computer gear into the hotel. Our sleeping system consisted of an insulated air mattress (Big Agnes and Exped downmat), an inflatable pillow from BA, down sleeping bags (Diane’s used the BA system where the air mattress slides into the sleeping bag making one unit). I tried it but I sleep on my side and couldn’t get used to it so I used a regular down sleeping bag on top of the air mattress.