Removing ads on apps that don't have ad-free version (e.g. Angry Bird) My disabled child likes this game very much. But he can't handle the advertisement. It is just too much for him. I would like to get Angry Birds ad-free. I would pay for it, but there's no ad-free version on the Play Store.

The device is not rooted, and I'm not going to root it. So if possible, is there any solution for non-rooted device?

.. several months later. Here is my solution

It seems impossible to disable ads on android games. Most of them are completely useless and some are glorifying war.

This is no problem for normal people.

For my disabled child this is information overload.

We bought an old standalone device. This kind of device where you need to buy games on cartridges. This solves my use case. AFAIK angry bird is not available for nintendo DSi, but other nice games.
If your device is rooted, install Adaway. It will remove ads basically everywhere.