I'd bust my activism moves and take it as an opportunity to get a win in for the animals if I was you.
If they've been doing this event like this before, they probably will just ignore the one off complaint. Students that haven't thought about the issue of zoos etc will just likely be pissed with you for being the cause of it getting cancelled and it'll push them away from looking into the issues at hand.
Not going at all just let's things go as it likes.
Best chance for a positive outcome is to get your neck out there on the day and get vocal!
I would think if you could find a way to weave in a presentation + fliers without looking like 'that one chick having a rage for attention', then as long as you catch their attention long enough, they will at least understand why you hold that position and hopefully you are persuasive enough to convince them to do some homework.
On that note - make sure you do end with a 'call of action'. When you end a speech or give out something. Tell them to join Unleashed or your uni's animal rights club for example. Don't let them just walk away without knowing what the next step they should take if they have a heart.
