I agree with taking water. It's always really expensive at these events. Before you take a cart along, check with the show. Houston Quilt Festival doesn't allow them on the floor unless you are a vendor. I prefer to take a tote bag. I've been banged with too many over full backpacks when people turn around. They seem to forget they have this big thing on their back! Another thing to watch is if you put your money in the backpack be sure to put it in a pocket that's against your body. I watched a woman take her wallet out of an outside pocket on a backpack, put it back and put the bag back on. As far as I'm concerned that's almost begging to have to lifted. For quilt fest, I have a badge holder that I hang around my neck and carry my money and credit cards there so they are always in front of me and next to my body.
Put on your patient hat because there are usually crowds and have fun!