Hello all! I'm seeking help in finding a bag that can handle my family of 4 while we are at the DLR and DCA. Now here's where this whole thing gets fun. I have a bad back so normal backpacks are very uncomfortable and cause massive amounts of fun nasty pain for me. I need something that isn't going to kill my back but that can hold 4 water bottles, snacks, and other important items for no more than $30 bucks. TIA!