Any game that offers a virtual currency purchaseable with real currency (be it coins, diamonds or energy rays) should be avoided. Especially if you have children.
One would need alternative App browsers for that, the default ones don't allow filtering out apps with in-app purchases since they are too lucrative. Here's one:
https://appapp.io/us/genre=Games;has_iap=false;supported_dev...
https://www.commonsensemedia.org/
Hopefully they will open a store once Apple allows 3rd party stores