Hi Jennifer!
Visiting the Walt Disney World Resort is such a fun family bonding experience, so I completely understand you wanting to be able to experience all of the attractions with both of your little ones! Luckily, many of the ride vehicles in the attractions throughout the parks allow three or more guests. Unfortunately, there are a few that only allow two guests per row or ride vehicle.
In Magic Kingdom Park, Astro Orbiter, The Barnstormer, Big Thunder Mountain Railroad (although sometimes three will fit), Buzz Lightyear's Space Ranger Spin, Dumbo the Flying Elephant, The Magic Carpets of Aladdin, Seven Dwarfs Mine Train, Space Mountain (allows one person per row, with three rows in each ride vehicle), Splash Mountain, Tomorrowland Speedway (although sometimes three will fit, but only one can drive) only hold two guests per row or ride vehicle.
In Epcot, Spaceship Earth only holds two guests per row, but the ride vehicle holds four.
In Disney's Animal Kingdom, Expedition Everest - Legend of the Forbidden Mountain and TriceraTop Spin only hold two guests per row.
In Disney's Hollywood Studios, both Rock 'n' Roller Coaster Starring Aerosmith and Toy Story Mania! only hold two guests per row. Also, since they are not open yet, I am not exactly sure what the ride vehicles will be like, but I believe that both Slinky Dog Dash and Alien Swirling Saucers in Toy Story Land in Disney's Hollywood Studios will only allow two guests per row or ride vehicle.
Of course, you can always ask a Cast Member at any ride about the best seating arrangement for your family. They are always happy to help! If you would like any more information on any of the attractions throughout the Walt Disney World Resort, make sure to check out the
full list of attractions!
Have a Great Big Beautiful Tomorrow!
-Lindsey N.