It's considered dinner. I'm not sure about the costumes, but I'm guessing they're wearing them all night and so will be 'dressed' at 4:30. There are later times available. Try calling back and talking to someone else. I just booked 5:45 for a party of 7 today. The first CM I spoke with told me 4:05 was the only thing available, so I hung up and called back. I told the next CM that we were attending the Halloween party that night and looking to dine at LTT, bingo, all sorts of times to choose from!