I know the pain with the marathon registrations. I have done 3 in the past and trying to get a group of 4 registered was very challenging.Honestly I don't think you'll have a ton of trouble for one of these at WDW, unless the system blows up again like it did with marathon registration last month. They typically have a ton of people at these events in WDW, plus with the reservation requirement you have quite an advantage. Just make sure you and everybody you want to buy for has your stuff linked in MDE to make sure there are no hiccups.