According to COPPA, you can only run contextually-targeted ads to the children. In order to server non-personalized ads, you have to send child-directed ad requests to your ad server (Google Ad Manager).
How to Send Child-directed ad requests?
1. Search Console:
If you are a publisher with a section of content or specific domains directed to the child, then you can tag the respective sections/subdomains using Search Console.
2. GPT Tag:
But for most of the sites, there’ll be only a couple of pages (if at all) with child-directed content and tagging an entire section or sub-directory (via Console) won’t be necessary. In this case, you can send child-directed ad requests via GPT tag from the pages where you wouldn’t want to run interest-based ads.
The rest of the pages can serve personalized ads as usual. You have to flag the ad request with child-directed status with the following API call:
Learn more about how to become COPPA compliant here.