Congratulations!
I don't know if you've ever done one of these before but be prepared for a heavy load and non stop reading. I've done 2 of them so far, the Connecticut Women's Expo. This event is huge, they hold it in the Hartford Convention Centre and there was an estimated 20,000 people turnout. (Not all of them wanted readings, thank the Gods!) We had a phlanx of readers there, about 14 of us. There were lines backed up out into the corridors for the readers. We offered $10. for 10 min, $15. for 15 min. We weren't doing any 20 min readings because there were
so many people who wanted readings. I had my handy dandy little farberware digital kitchen timer and that thing kept me on schedule. It was hoppin! I don't seem to have any trouble reading accurately in these situations, for some reason I'm more energised at the end of one of these than I am when I get there, but some of the readers were seriously tired out.
Be prepared!
Have enough water on hand so you don't dehydrate, and you may want to pack something to eat in case the turnout is very heavy. Promotional materials will help you, even if you can just run off some flyers telling folks who you are, with contact information for setting up future appointments. You can get good repeat biz from an event like this.
I had the best time, but it was
busy.
Wishing you all the best and lots and lots of fun!
At other venues here, I have averaged over 10 readings a day (hundreds of attendees - and not the only reader). I have heard that they get an average of 6000 attendees at this event, and I am concerned that I am the only reader (despite what someone else told me) because of how she has interacted with me... like she doesn't know how to deal with a reader (like where to put me. She never said she would put me with the "other" readers, or something like that!). 
Lyn
The sitters at Expo are lucky to have such a great reader as yourself!