How can I best showcase my web based service to up to 12000 potential customers as an exhibitor at a trade show before my startup has launched?

My website will be about 75% complete, but I am not able to actually take on customers for other various reasons until about 6 weeks after the show. How can I still be confident in potential customers on the back of this? I am exhibiting at a gift and homewares event as a startup which can help all retailers attract more customers and sell more products (ie I am not competing against them) and have been selected to attend as a startup by the organizers as they see my service as a perfect fit. I am feeling very rushed, however, I know that attending in a years time will be too late for me. This is too good of an opportunity to miss and I need to form a solid strategy around my attendance to maximize effectiveness.