Blocking ads which have adult content

The first thing I would do is contact the developer of the app and ask them why they are displaying inappropriate ads to children. The developer is the one that is making money on the ads displayed, so they should be held responsible.

You can also report the app at https://reportaproblem.apple.com and choose report offensive content. It is typically for the app content, but I would use it to report ad content from the app as well.

I would caution against using Ad Blockers that can be purchased, as we have seen many problems with those here on these forums.

Free games are often funded through advertising that will be displayed during gameplay. However, many free Apps that are funded through advertising offer an in-App purchase to suppress unwanted advertising.