Child specific sites would not add the header. Anyone else could. I add it to my hobby sites. Some porn sites already add it to their sites [1]. Shodan can't reach my sites.

Add it to any site not specifically meant for children, that is totally fine.

[1] - https://www.shodan.io/search?query=RTA-5042-1996-1400-1577-R... [ Follow Links At Your Own Peril ]