As you’re only selling it to the parents, I don’t think you have to worry about it…. if you were mass producing it, or selling it to third parties it would be a different story.
If you REALLY want to cover your ass, and put something in the contract, I would just say something along the lines of “the client claims all responsibility for any copyright infringement” (you’d want a para-legal or lawyer to look that over of course) But in my opinion, putting that in the contract may be a turn-off, and, probably unnecessary.
For a longer, more specific answer, refer to the link posted in the similar thread: http://www.videomaker.com/article/14537/
And of course, I am not qualified to give legal advice, and do not claim any responsibility for you getting sued =P
Good luck with your endeavors
