Karla--your printer should not have any trouble with cardstock-it is a little thicker than regular paper, but still very flexible and should print fine. If you can put photo paper through your printer, then cardstock should be no problem for you.
Good luck--I am so excited for you!!!! If you have time, set your table up at home and take pics of it. If you look at the pictures on the computer, then you can see things that might need to be changed (there is just something about looking at a photo that you notice things you do not see in reall life-I try this trick with my quilts too) It will also make your set up go faster the day of the craft sale if you can just look at your pics and know right where you want to put everything!!