The first time I traveled alone after my son was born I was so excited for the relative peace and quiet and alone time that an airplane would afford. And then I sat in front of a toddler watching Mickey Mouse on an ipad without headphones. I felt like crying.
We got these and they worked. If you go to amazon and put toddler headphones in the search bar you will get plenty of options.
http://www.amazon.com/Kidz-Gear-Wired-Headphones-Kids/dp/B00AXE9B6M/ref=sr_1_2?ie=UTF8&qid=1387331752&sr=8-2&keywords=toddler+headphones