Hiya, Barbara!
Welcome to planDisney! Oh boy, it sounds like you will have a lot to celebrate. Not only are you going to be at the Happiest Place on Earth very soon, but enjoying two birthdays while immersed in the magic sure sounds like a hot diggidy dog vacation!
Barbara, while I can't say for certain what will be available on the day of your visit, as merchandise can change as can stock, I can make a few recommendations for where to look. The first place I recommend is
Disney's Wonderful World of Memories in Disney Springs. Here is where treasures unfold of a variety of different styles of Mickey Ears and other thingamabobs for special vacations like birthdays. You can also try the
World of Disney, also in Disney Springs. Very often you will find a large selection of Mickey Ears and hats, including one of the Happy Birthday Ears. In Magic Kingdom Park, I would recommend
Curtain Call Collectibles which typically has a wide variety of Mickey Ears and hats and it's possible you will find them there.
I have seen them at the parks somewhat recently, so I am wishing upon a star you will find them at one of these locations on your visit. If you keep searching into the unknown and are unable to locate them, I would recommend asking one of the Merchandise Cast Members and they may be able to direct you further.
I hope this helps you, Barbara, and you are able to have the birthday celebration of your dreams. If you need anything further, stop back here to see us and we will be glad to help.
See ya real soon!
Keri