I made ressies for the hoop dee doo show for our upcoming trip in late Nov. I also ordered my DDE card 3 days ago. The CM asked if I was on a dining plan when I made the ressies for the HDD and I said that i'm expecting the DDE card soon. The CM didn't say anything more and I went ahead and paid the upfront cost for the HDD show. I wanted to know how do I get my discount on the Hoop Dee Doo show when I already paid the full price in order to make the ressies?? It's the 9:30 show so i know I qualify for the DDE card discount. Do i call back Disney dining once i receive the DDE card in oder to get my discount or just show it to them when I check in to see the show??
I just called and said "I have a DDE card." He said okay and gave me the discounted price. He never asked for the number either.
Just that we would have to show the DDE card when we go there (though we never had to anyway) and if we couldn't provide it then we'd be charged the extra. 
