I looked at the flier for your show and it looks like a very casual show for charity. In my opinion, these are the best shows. You get all types of cars, so there's plenty to look at, and something for everyone. This is a people's choice show, not a concours event, so you don't have to kill yourself to prepare. Of course, you want the car to be impeccably clean, both inside and out, as not to embarrass yourself.
I always try to arrive very early. The first cars in typically get placed at the end of the row for their class. Those are the cars that get noticed, as opposed to the ones jammed in the middle of the row.
Invariably, something will happen on the way there, so you want to have (at minimum) spray detailer, several microfiber towels, glass cleaner, tire dressing and an applicator, a lint brush for the mats, carpet and convertible top and some bug and tar remover.
Take a good look at the car when you get there and remove any bugs or tar you've collected. Remove everything from the car. You don't want any "stuff" inside detracting from its looks. Think of little things to make it present well, like adjusting both seats exactly the same way. If your mats aren't perfect, take them out and stow them under the car. Wipe down the whole car with the spray detailer (including the wheels), clean the glass inside and out, run the lint brush over the carpet, top, etc. to pick up any stray lint and
lightly dress your tires (including the tread). When you're done cleaning, put your supplies in a Rubbermaid container or something and set it aside. Don't throw your cleaning supplies back in the car. Now, relax and enjoy your day.
Since it's a people's choice show, I would show the car with the top and windows down, unless it's too dusty. People love convertibles. Also, as you're preparing the car, don't forget to thoroughly clean both luggage compartments, as most people show their cars with the hoods and trunks open. If you do show it with the luggage compartments open, remove both luggage compartment light-bulbs so you don't kill your battery.
Don't forget to pack some cold drinks, sunscreen and a couple of folding chairs for yourself and your wife. If you plan to stay for the whole event, it can be a long day.
Now, if you were entering a concours event...well, that's a whole other story. Here's a 68 page pdf on how to prepare for one. You might want to glance at it just as a reference for what you want to address before the weekend.
http://www.brackenrig.net/Concoursstuff/concours101.pdf
If you enjoy yourself and decide to show the car regularly, I would have one of those little sign boards made so that everyone can read how special that car really is.
Good luck!