The film will be shown exclusively at ODEON Cinemas in more than 100 locations across the UK before selected family movies until the 23 December 2011.
The latest release, which is based on a true story, sees Wenlock and Mandeville help a school create a library bus after their library is destroyed in a storm.
The mascots are joined in their new adventure by CGI animated versions of British athletes Louis Smith, Zoe Smith, Victoria Pendleton, Shelly Woods and Tom Aggar. The film also includes narration by TV and film personality Stephen Fry.
The film's writer, British author Michael Morpurgo, said: ‘We have these extraordinary characters Wenlock and Mandeville who are not only encouraging young people to take up sport, but are inspiring the next generation of story tellers and writers.’
The fourth and final film, which will also be shown in ODEON Cinemas, is scheduled to be released on 1 May 2012.
The exciting news comes hot on the heels of the launch of the official mascot song 'On a Rainbow', featuring McFly star Tom Fletcher and his sister Carrie.