I would say it depends on what you plan on shooting. I'm bringing down a 50mm and 85mm prime on my next trip. On full frame, the 50 will cover dark rides nicely, and the 85 will be good for close ups, like on Hall of Presidents, or dark rides where you need the extra reach to get a certain AA. My walkaround lens is a 24-70 f/2.8 though, which is almost like a prime in terms of speed. So, I would bring probably the 24 and the 43. Hope this helps!
)(although I don't love this lens as much as the 50mm)



) I like shots of the kids that put them in their environment- fast wide lenses do it for me.