Disney is jumping on the portable-video bandwagon, expanding its line of media players and offering movies on memory cards. On Tuesday it announced an upgraded version of the Disney Mix Stick music player, which features more memory; a mini version called the Disney Mix Micro; and a multimedia version, the Disney Mix Max Player, which plays music and movies and displays photos. Disney has taken SanDisk’s approach to media players by offering expansion slots for memory cards to increase device capacity rather than equipping the devices with large internal memories. And the company is selling postage-stamp-size cards with Disney content already on them.