From ARRL News:
Kids Day runs from 1800 UTC – 2359 UTC. Operate as much or as little as you like.
The event is designed to give on-the-air experience to young people, to foster interest in getting a license of their own, and give older hams a chance to share their stations and love for amateur radio with their children. You can share the excitement with your own kids, grandkids, a Scout troop, a church, or the general public!
All participants are encouraged to post their story and thumbnail photos to the Kids Day Soapbox page. Tell the world about your operations, the fun you had, and the contacts you made! Remember, ARRL must have a completed release form in order to include youth photos (younger than 18 years of age) in ARRL publications.
There will be a second ARRL Kids Day on June 21, 2025.
More information, including frequencies, suggested exchanges, and how to download a certificate, can be found at Kids Day.