Welcome to planDisney, Jasmine. If you want adventure in the great wide somewhere, then a 5-day trip to The Most Magical Place on Earth is certainly the way to go. I can understand the intense excitement (I mean, you're going to Walt Disney World!!!) and overwhelmedness (I mean, you're going really soon!). But as Mary Poppins once said, “Everything is possible, even the impossible.” Let me suggest some things that'll help you make the most out of this trip.
You're going to want to purchase tickets and then make reservations at the Theme Park(s) that you'd like to visit. With a 3.5-year-old pirate and an 18-month old princess, I think Magic Kingdom Park should be top of your list. Not only will your kids be in awe of Cinderella Castle, but they'll be able to see some magical friends in Mickey's Celebration Cavalcade. There are many kid-friendly attractions, like "it's a small world," Prince Charming Regal Carrousel, Dumbo the Flying Elephant, and Peter Pan's Flight.
If you'd like to do multiple Parks, then Disney's Animal Kingdom is wild, beautiful, and fun. The kids will love Kilimanjaro Safaris, A Celebration of Festival of the Lion King, and the wonderful Disney KiteTails. EPCOT is also great for young kids, with attractions such as Frozen Ever After, Journey Into Imagination With Figment, and The Seas With Nemo & Friends. You can't go wrong with any of those Parks.
I'd encourage you to download the My Disney Experience app so that you can use Disney Genie. This free service can help you plan your day in a way that is catered to you and your family.
As a dad to two young kids, I've learned a few important lessons along the way: Bring your own stroller. Not only is this essential for those tired little legs, but it's also a great place to store your belongings. Bring your own snacks. You never know when that next meltdown will come (from parent or child!). A snack can be a lifesaver! Sometimes all one needs is a bit of energy. So bring plenty of snacks. Slow down. You can't do everything. Amidst all the excitement and busyness, take time to stop and relax. Let the kids just run around, play, and explore. Take lots of pictures. When you get back home, there's nothing better than sitting down as a family and looking back at all the memories you've made together. Since your hands will be full, you might even want to consider purchasing the Memory Maker.
I hope you have an enchanting trip, Jasmine.
Mike