What to wear to an interview for a zoo/wildlife volunteer position?

I applied to volunteer for a non-profit wildlife center and my interview is tomorrow. What do I wear to it? I dont want to dress too nice or over-dressy, yet I dont want to be too casual either. The other job I work at required me to dress nicely, but with the wildlife center I would work with the animals in a uniform, so I don't know what to base my interview dress code on.What to wear to an interview for a zoo/wildlife volunteer position?
Considering the position, I would suggest a nice pair of khaki pants, loafers or other such shoes, and a golf shirt or such. a jacket would be nice to go over the shirt, all clean and pressed.