I took my Mom to the IQS Show in Rosemont last month, and rented her a wheelchair. I worked out pretty good...Some of the booths I didn't dare enter with the chair. So some we parked it and she went to look at what she wanted. When we were looking at the quilts, we did get a bit better view because I was able to push her up pretty close.
Just make sure that you have a tote bag with longer handles so that you can attach to the back of the chair.
If you don't know how to control one of the motorized carts, I really don't know if it is such a good idea in the crowds....you will have to judge. I didn't get it for Mom because I knew it would make her nervous trying to drive it in the crowds.