Some examples:
- I was so happy how you did your homework today without asking.
- Thank you mom for cooking my favorite meal today.
- Thank you "brother" for letting me borrow your favorite toy.
- I love how you said such a thoughtful prayer last night.
A modified version for older kids would be to make a Gratitude Calendar. Print each family member a template of the current month's calendar. Each day they must write something that they are thankful for.