It’s a minefield really because of COPPA. I have two such games and I have removed any ads from them to be safe. Better use IAP but be prepared to refund if someone’s child buys too much by accident.
All i can say if you choose Appodeal and turn on option “For kids only” you will still can receive porn-like, erotic ads i have received several 1star reviews for my kids apps for that…don’t know the situation right now, but i’m not sure they can really handle it