Top picks to pack: Stretchy lizards, Hot Wheels cars, sewing cards, lollipops, mini cereal boxes, and books with felt or magnetic pieces. Also, if you’re toting a car seat, consider a travel tray that snaps onto it, as younger kids may not be able to reach the seat-back table. What not to pack: Legos, puzzles, bead kits, and mega packs of markers and crayons—you’ll constantly be reaching under the seats for the Lego man’s head and marker caps.