For parents, one great resource for this is Emeritus Philosophy professor Dr. Tom Wartenberg who posted 2 excellent Youtube videos about he and his university level Philosophy students teaching K-6 elementary students philosophy:
Dr. Wartenberg has a great book for parents/guardians/teachers teaching kids Philosophy/Critical Thinking: Big Ideas For Little Kids: https://www.amazon.com/Big-Ideas-Little-Kids-Philosophy/dp/1475804458/ref=sr_1_15?dchild=1&keywords=philosophy+for+kids&qid=1626797106&sr=8-15
Another book I have used in the past as a teaching tool is Philosophy For Kids by David White: https://www.amazon.com/Philosophy-Kids-Questions-Wonder-Everything/dp/1882664701/ref=sr_1_4?dchild=1&keywords=philosophy+for+kids&qid=1626797106&sr=8-4
These are great resources for educators, but also for parents who want to engage their children in critical and creative thinking discussions.
I think the question of secular kids implies the question of facilitating kids to be creative and critical thinkers, so this might be a fruitful avenue foy you to pursue! Two sites I wanted to mention on the Philosophy for Kids topic are:
1) Teaching Children Philosophy is a resource for parents and educators that grew up around Dr. Wartenberg’s program that I mentioned above over the last decade. It’s wonderful: https://www.prindleinstitute.org/teaching-children-philosophy/
2) Philosophy For Children from the University of Washington. This is a great resource page on their site: https://www.philosophyforchildren.org/resources/lesson-plans/