Almost everything fits 3 in a car (even if it doesn't look like it) so it's easier to list the ones that don't:
1) Barnstormer
2) Indy Speedway - someone have reported having 3, but we never tried it so I can't say for sure
3)Rock 'n' Roller Coaster (non-issue for you)
4) Expedition Everest (non-issue for you)
5) Kali River Rapids - the rafts fit a lot more than 3, of course, but only 2 seats are together so you wouldn't be right with one child
6) Buzz - fits 3, but only 2 guns
7) Toy Story - again only 2 guns per seat, not sure if 3 can fit or not as we all insist on our own guns
Lots of rides that look like only 2 fit across, fit 3 fine.
Examples: Haunted Mansion, Dumbo, Peter Pan, Winnie the Pooh, Splash Mountain, BTMRR
Let me know if you have questions about specific rides.
