My tip is to figure out where you'll eat when you don't get in. IF a walkup is going to be accepted it'll be most likely to work if you show up at least 20 minutes before they open and ask then but I wouldn't count on it happening at all. If it does then you'll know that you have received pixie dust and can really enjoy yourselves. If not, you'll at least be prepared and it won't put a damper on your day.