If I were the director I would realize that we only have probably one shot at this so I would make one movie. Start with the first five books, end with the last five, and fill in the middle with the best of the rest. Chances are the budget wouldn't be a lot so I would consider animation, not cartoony animation but Clone Wars-esque animation with lots of action. This way you don't have to worry about horrible looking andalites and flash light dracon beams because of lack of money.
