Yep. When its done once, dozens will think it's a dandy idea and try to follow.
I also wonder how the OP will deal with those of use who just download waypoints and don't have the cache pages. What is to keep this kind of cacher from wandering on to the property in search of the cache not knowing about the appointment restriction? Is he going to delete the legit finds? If he does that won't sit well with a lot of locals. If he doesn't then what will keep others from finding the cache without an appointment and claiming they didn't know?
This is exactly what I am worried about. I generally keep 200-500 waypoints in my GPSr and don't always have descriptions available to me. I would have no way of knowing that this is a night cache. Also I really am nervous caching on private property not knowing the owners, property lines and potential for problems were I to cross property lines. I think the best idea would be 2 caches, one a micro with the combination to a lock or key to a locked gate and a description of the 2nd night cache. Probably should have boundaries marked out.
I would also suggest a conversation with a lawyer and insurance agent about liability issues in your area with this type of cache.
Just my $.02 and probably worth a lot less
droid81