There are a lot of problems with children's apps, very strict rules.
If you're an independent developer, it's better not to go there, this audience is very hard to monetize and has very low retention. Without recognizable brands, you have nothing to do there.
You need to familiarize yourself with google requirements for such apps, fix everything and post an update.
If you have only Admob and no analytics you need to disable user data collection, disable personalized ads. Set a restriction on advertising content by age and re-fill the google user data.