Bring address labels! That makes it so easy to register for all the give aways. I had labels printed with my name, phone number and email just for booth give aways.
The baby may sleep the whole time but then again may decide the noise and stimulation will be too much. The fact the grandmother is the sitter doesn't mean she can't hire a sitter. I baby sit my infant grandson during the day but I use a sitter for times it will be better for him to stay home when I want to go somewhere. I would want to spend the day at an Expo not just a couple of hours so maybe you can go back by yourself the next day.