Hi
Nina!
Congratulations on your upcoming nuptials!
Unfortunately your group won't be allowed inside the theme park in formal attire. The only exception to this rule is if you are having your photo shoot done through
Disney Weddings Photography (DWP). You might want to book a photo shoot through them. In addition, consider having your pictures taken at any of the wedding gazebos on property. I recommend trying for pictures in the vibrant BoardWalk Gazebo at Sea Breeze Point with spectacular views of Lake Crescent and its surroundings. Do keep in mind that if there are other couples having a photography session done by DWP and you didn't book through them, you'll have to wait for that session to conclude before you can access the location.
If your goal is to have the photos taken inside Magic Kingdom and you won't be using DWP services, consider changing into less formal attire before heading to the theme park. For example, you could wear a cute white sundress with a flower behind your ear. Your husband could wear khakis and a nice crisp shirt. The wedding party could be similarly attired. This would be a more casual look, but still bridal. Pictures by the Plaza Rose Garden might be especially nice. If you are bringing your own photographer and you want pictures taken inside any Disney Theme Park, you'll have to provide theme park tickets for your photographer as well as anyone else joining you during the photo shoot.
Please let me know if I can answer any other questions for you. Once again, congratulations and enjoy a most memorable wedding celebration at the Walt Disney World Resort!