Hi Melissa, and welcome to the Disney Parks Moms Panel!
Hear ye, hear ye! The royal sisters of Arendelle are pleased to announce that they will soon be greeting Melissa and her family as their honored Guests. And all the kingdom will rejoice!
Seriously, congratulations on securing a FastPass+ selection to meet Anna and Elsa. It's literally one of the hottest tickets in the kingdom, and you're in! And a fabulous dinner at Disney's Grand Floridian Resort & Spa after that? You're certainly planning a magical day at Walt Disney World.
You should have plenty of time to make your dinner reservation after your royal audience with Queen Elsa and Princess Anna. Just to be on the safe side, I'd plan to arrive at Princess Fairytale Hall as soon as your window opens (you can actually enter up to 5 minutes early). From there, exit the Magic Kingdom and take the boat over to the Grand Floridian. In my experience, it's the quickest way to get there since the monorail makes several additional stops on the Resort loop.
I'm so excited for you to get a chance to have these great experiences, Melissa! Please stop by again if you have any other questions, and have an amazing Walt Disney World vacation.
Keep Disney Dreaming,
Kathy K.