You're presumably operating out of Estonia, so American laws like COPPA[1] probably don't apply to you (disclaimer IANAL). I have no idea if the EU and/or Estonia have counterpart law(s).

Nonetheless, the complete lack of a privacy policy at the time of writing this comment is concerning particularly because you are (explicitly!) interacting with and handling data concerning children.

I would strongly advise consulting with a lawyer about what legal measures you need to comply with for a service like this.

[1]: https://en.wikipedia.org/wiki/Children's_Online_Privacy_Prot...