As a father I can't imagine ever leaving a 3-year-old alone with media so they can be 'independent'. If for no other reason, that's an age and developmental stage where media should be almost nonexistent in their lives.
The same way you might say to a kid, "pick out the book you want me to read to you off the shelf" this is something like, pick the video we are going to watch together.
Besides, non-interactive, low-stimulation media with a plot line and simple dialog is not on the same level as giving your child a tablet and letting them have at it.
My real concern with this project is the amount of time the builder spent away from his children. Now I get it that some folks(dads on the spectrum?) might feel their best contribution to their child's development stems from something they build in the lab but your children are only young for such a short period and taking time away from them to build a custom electronic solution seems narrowminded and selfish.