Photography questions for an expo? :D

So, I'm going to the Portland Expo this weekend, and it's my first time going to something like this :D I was going to bring my camera and I'm not sure what my set up should be. I have a Canon t4i/650D body, and my 3 lenses are the 18-50mm, 55-250mm, and 40mm pancake. I was thinking the pancake and longer zoom in case I can't close enough, but my 18-55 is my only thing that's remotely wide angle (the 40mm has 1.6 crop factor, so 64mm :) ) soo.... what do you all with spare lenses bring? Should a prime and long zoom be enough?

And also, what is a the protocol about pictures? Just the normal ask if its ok first? Is there any type of thing where it's just a general 'no no'?