iTunes movies from iPad 2 to iPad 4?

Apple answers thist question: "If I buy a new iPod with video capability or an Apple TV, will I have to purchase the movie again?" with the answer "No.", here:

http://support.apple.com/kb/HT1906?viewlocale=en_US&locale=en_US#faq35

I have my third iPad now. On my second iPad I bought some movies to my children. How can they watch he movies on my new iPad?