Unless you are planning on jumping way up or way down in weight, your arrows you have now will fly good enough out of most bows especially at the short shot distance at KZoo, to see how a bow shoots. That said, most of the bowyers there will have some arrows to try with their bows, but you may have to wait your turn to use them. I usually take 3 arrows of my own with me. Either way, I would bring my tab or glove for sure.
As far as if they will let you shoot them, all of the folks that I have ever met there was more than happy to let me shoot their bows, even if I wasn't standing there with bow buying cash in hand(joke). Everyone is usually Very friendly and willing to answer all your questions or let you try out their wares. You will have a great time!