Yup, unless you already have the proper paperwork, taking them back across the border will be illegal. I also do not believe that animal sales will be the primary focus of this show, this will be a special, one-time benefit exposition to raise funds and awareness of the issues facing the reptile industry on behalf of PIJAC and USARK.
I don't think that CITES paper work takes as long as it used to, but it still takes some time to complete. You might want to start researching it now so that you'll have everything you need ready by the time the next show in Tinley park comes around this up coming October 9th and 10th.
(CITES: Convention on the International Trade in Endangered Species)