I'd come here and look to see if someone posts a link, but i believe if you go to the member event calendar (not sure exactly what it is called) it will bring you to the moonlight magic events for the date you want, when you select it might bring you to a link for signing up (when it opens).
You can see what i mean when you look to see about the last MK event that is coming up on 2/6 - check out the calendar.
Some here reported receiving an email with a link, many did not get the email until later in the day. From the looks of it even though the MK event is next week - there is space available, so it hasn't sold out.
I'll be looking to do the AK one for April which is opening registration next week. I am hopeful that as long as i am on the first day i should have no problem registering my party.