Absolutely!!! One kit per family or classroom is all you need. I am happy for educators and therapists, etc to use the materials year after year. The pdf's are created with this use in mind, both in color and black and white.
I would just ask that you encourage other educators (the ones that will see the awesome-ness you are generating with your set and that might want to begin working with them as well) to purchase their own Time-In Toolkit and support the work Generation Mindful is doing in the world. We have purposely designed the ToolKit to be inexpensive to allow as many people as possible to have access to them. Thank you for asking!
For families with multiple siblings, one set is all you need!