This is interesting, and both the linked article, and the comments which follow, are fair and balanced.
I've not been to one do these events, but must admit to finding the way in which they are marketed rather off-putting - they really are presented as a sort of bacchanalian night out, rather than, as is the case with most late night openings, a chance to see the zoo in a different context. I guess they're all a part of the firewalk / streak through the zoo pattern. If money is raised to the extent suggested, then that is excellent - but hopefully money isn't the only factor.
Other zoos do have late night openings which can be wonderful - Colchester's is always excellent. An extra feeding-time talk at the tamandua enclosure isn't going to attract the same crowds that will gather for a silent disco or a beer tent, but I'm pretty sure that the late-night crowds at Colchester have never cracked glass / poured beer on a tiger / punched a bird.