This was a huge problem for us because we have boosters back there. Buckling in for the kids was such a task because the buckle "turtleheaded" into the seat. My fix for that was to get seatbelt extenders (the 5 inch rigid) This helps the kids easily buckle in and out without wrestling with the "turtleheading". Hope this helps:

Kia Carnival Seat Belt Extender
This Seat Belt Extender is designed to fit in your Kia Carnival.
