I'll definitely try out posting on FB groups, that's a great idea. I think general target groups are families with young kids, or people interested in language learning.
Do you have a link to the app that you made? I'd love to check it out.
Well, I do have small kids who learn languages. But for one thing, you don't come with name brand backing like Pink Fong or Ryan's Toy Reviews, so you'd have to stand out from them. Sites like Cocomelon/ABCKidsTV are posting videos with over a billion views. I guess off the top of my head, a lot of parents direct their kids to YouTube, and then look for apps when they need something more interactive.
Maybe one approach is to pay influencers, though the topic of influencers varies widely.
Another approach is to do what a friend does and work with a major influencer. Here's an example of his app: https://play.google.com/store/apps/details?id=com.astro.didi...
They made a great game, distributed by a major media company, and a smaller YouTube content creator. The game elements weren't the main selling point; the players just wanted a "Didi and Friends" game. But it was a lot of fun for the kids and easy purchase for parents.