Hi Doug!
Walt Disney World Resort is great about accommodating offsite guests that need to be dropped off at any of the four theme parks:
Magic Kingdom Park,
Epcot,
Disney's Hollywood Studios and
Disney's Animal Kingdom. There are designated Drop Off and Pick Up areas at each park, and the Cast Members at the park entrances can help direct you to these areas. There is also plenty of signage to help direct guests to the Drop Off areas.
When you enter the Guest Parking area for each theme park, all you need to do is tell the Cast Member that you're dropping off guests. They will direct you to the drop off location for that park. Epcot, Disney's Animal Kingdom Theme Park, and Disney's Hollywood Studios have drop off locations located a short walk from the entrance. When visiting Magic Kingdom Park, there is not a drop off area at the actual park entrance. Guests will need to be dropped off at the Ticket and Transportation Center, and then take the Monorail or ferry boat over to Magic Kingdom Park.
Once your family members are done with their day of fun at the theme park, simply return to the same area where you were dropped them off to pick them up!
I hope this information is helpful, and that your family has an amazing visit to the most magical place on earth! - Diane W.