Hello Angela!
I'm so excited for you to be bringing your li'l Mouseketeers to Walt Disney World. It will be here before you know it and planning is half the fun. Spending 3 days at Magic Kingdom will allow you to take your time and enjoy the many aspects between entertainment and attractions. I would advise visiting Magic Kingdom early and late in your trip, as President's Day and the days directly surrounding the holiday will be busy at Magic Kingdom.
Character Dining is an excellent way to visit with characters and obtain their autographs. Because Advance Dining Reservations become available as early as 180-days in advance, I'd recommend setting up your reservations now. You can do so
online or by calling 407-939-3463. You cannot go wrong with any of the character dining experiences, but I encourage you to check out the typical characters at each meal. Classic characters, including Mickey Mouse, can be found at Chef Mickey's at Disney's Contemporary Resort. On a Magic Kingdom day, you can either walk or ride the monorail over to the resort. It's very close by and a great character meal!
If princess meals are desired, you can continue to look for openings at Cinderella's Royal Table located in Cinderella Castle. This is typically the ultimate in character meals but a hard reservation to obtain. A good tip is to visit Cinderella's Happily Ever After Dinner at 1900 Park Fare, located at Disney's Grand Floridian Resort & Spa. It's also accessible via the monorail, just outside Magic Kingdom.
I'm limited in space, Angela, but I'm happy to expand on any topic you wish to discuss! Feel free to write me back.
Best wishes,
Sherri