I can definitely feel your pain when it comes to those awful ad-full games advertised as suitable for kids. On the other hand. It's really hard to make money in this business w/o aggressive monetization practices. Sadly not many parents are willing to pay for this kind of games which is probably why you don't get much quality content.
This will be a shameless plug here, but feel invited to check out Pora Ora series. We don't have ads and we are free to play (the one IAP being unlocking the whole content about half way through).
One of our games is Pora Ora: Leapfrog - a multiplication game for children. It provides a fun, motivating and effective method for perfecting the times tables, with intelligent progression and engaging gameplay.
Just look for Pora Ora: Leapfrog or Pora Ora: Spellfire (a words game) on google play or apple app store.