Assalamu Alaikum
When children are younger, they absorb information very quickly and their minds are still developing. You should limit their screen time, especially today when children are over exposed to the internet. It definitely will start affecting their behavior. It's not sinful for them because they are too young, but what they see may desensitize them in the future and effect them. As their mother you should try to teach them things which will help them in their future instead of allowing them to mindlessly waste their time and energy on a screen. There are a lot of ways to be creative with them. I know it's easier for moms to be more productive when their children are busy, but they can get addicted to watching things online, so it is better to find healthier outlets for entertainment.