how can I sync a movie downloaded on itunes from my personal computer that is authorized for my daughter's ipad, but the purchased movie was done under my apple id

To start off, I absolutely do not understand iTunes. I feel that with every new "upgrade" it becomes more difficult to use.

We have 3 apple ID's for our home to make syncing easier and not have complications with devices. I have a window's computer with itunes which is "authorized computer" for all 3 apple ID's in family (mom, dad, child). We purchased a DVD with digital copy, installed and redeemed the code for the digital copy. However, it would not allow me to "redeem" on my child's apple ID. therefore, the digital copy went into my apple id. Now I can not sync the movie to my child's ipad/apple id. How can this be done? Please help! I know it can't be that hard, or is Apple just making iTunes worse and worse.