Children are by nature a bit narcissistic and they see things in black and white. The Caleb and Sophia videos feed them with the idea that their every little movement can make the god of the universe happy or make him very sad. This puts tremendous pressure on them to comply with rest of the Watchtower programming that is foisted upon them.
If you can't tell your Mom outright that you don't want your kid subjected to JW videos, you could tell her that you've heard that it's not wise to use the TV or kids videos as a babysitter even if the videos are supposedly educational.