Hi Leslie! For your situation, it sounds like you have already decided that Magic Kingdom is a must-do. Great choice! This is my favorite theme park and in addition
attractions at Magic Kingdom, there are some unique
entertainment opportunities that makes your visit to Magic Kingdom special. Starting your day off at Crystal Palace is something I do often so again, great choice!
Now you have a decision to make as to whether your daughter wants to include Epcot into their itinerary. If you have a park hopper ticket, I would strongly recommend that the girls visit Epcot. If you have base tickets, I would suggest your daughter and friend review the
attractions at Epcot. I'm sure they would especially enjoy the newly refurbished Test Track and Soarin'. They may also find it fun to dine in other countries. As a side note, I brought my 16 year old daughter to Disney a few months ago with friends and they had plenty to do during the day and we didn't even have time to visit World Showcase!
My suggestion would be to spend a day in each of the parks. And don't worry, girls have a way to make anything fun when they are together!