Hi Aaron,
It's great to be back answering questions on the Disney Parks Moms Panel again!
I can't think of anywhere better than the Walt Disney World Resort to celebrate two milestone events in your family.
In order to get some lovely photographs in the Magic Kingdom without many other Guests in the background, I would highly recommend making an Advance Dining Reservation for the earliest time possible at one of the restaurants inside the theme park. Making sure that you do not choose a day when there are morning Extra Magic Hours at the theme park.
Arrive at the Magic Kingdom as early as possible on the day of your reservation (an hour beforehand if at all possible) and get in the line of Guests with early morning dining reservations as soon as you can. This should ensure that you will be some of the first Guests to enter the theme park. Once you are allowed to enter the theme park, I would recommend that you walk right down Main Street U.S.A. to the last PhotoPass photographer before Cinderella Castle (who is normally found by the statue of Walt Disney & Mickey Mouse holding hands). This should allow you to get some great family photographs without hardly any other Guests around.
Alternatively, you could arrange for a family portrait session with
Disney Fine Art Photography & Video. This is a more costly but at the same time, more professional option. Although it is not possible to have the session take place at the Magic Kingdom, you can choose from many other locations including Disney's Hollywood Studios, the World Showcase at Epcot and Disney's Animal Kingdom. My fellow Moms Panelist Krista had some lovely photographs taken at the Morocco Pavilion a few years ago.
I hope that this information has been of help Aaron and wish all of the family a magical holiday filled with memories which will last a lifetime!
Emma