We always take a small backpack to theme parks. At disney, it's usually a poncho and umbrella (cause with florida weather it could rain at any minute), a camera with extra batteries, a hard sided water bottle for refills, extra socks, one of those sprinkler fans during warm months, wallet with all the important cards, brush and small towel for water rides and a few snacks. Plastic baggies are important for wet items or to prevent items from getting wet. We carry the bag also for small things we might pick up throughout the day and its usually not heavy or a bother. Even so we switch throughout the day, I'll wear it for the first half of the day and someone else for the second half.