Urgh, I know, it's so frustrating. From everything I've read, there really IS Wishes, it's just Holiday Wishes, and they've yet to set a time for it. My suspicion is that once they set the time, the dang party will be bookable -- but until then I'm stuck ranting here on the boards about it! LOL!
If there was no Wishes at all, I would be less frustrated... of course I wouldn't be trying to book the party then. (I suspect it would be greyed out on the calendar like it is for Grad Night in May.)