Hi Sarah,
Thank you for visiting the Disney Parks Moms Panel with your question. How exciting to be planning a trip on which you get to introduce both your boyfriend and your daughter to Walt Disney World! Be sure to get a "First Visit" button for each of them. These are available free of charge at Guest Relations and many other locations throughout Walt Disney World.
For your day that you are with your boyfriend only, I suggest
Epcot. You can spend the morning experiencing attractions in Future World that might be too thrilling for your daughter, such as Test Track, Mission: SPACE, and Soarin'. A casual stroll around World Showcase taking in the international pavilions and entertainment acts along the way is great way to spend an afternoon. You can have a meal at one of the fabulous restaurants there, such as Chefs de France in the France pavilion or the Rose & Crown Dining Room in the England pavilion.
For your day with your daughter, I would head to
Magic Kingdom. With Cinderella Castle as the centerpiece, Magic Kingdom is iconic. With a child her age, you can spend lots of time in Fantasyland on attractions such as it's a small world, Peter Pan's Flight, and The Many Adventures of Winnie the Pooh. She can meet characters at Magic Kingdom, such as meeting Mickey Mouse at Town Square Theater or meeting princesses at Princess Fairytale Hall.
Although your daughter is a little younger than preschool age, I suggest that you visit the website about planning your trip to
Walt Disney World with preschoolers. There, you will find helpful tips for your visit with your little one.
I hope that these thoughts are helpful for you, Sarah. Please let us know if you have any further questions!