I did an exercise with my kids (ages 4 and 3) which I think anyone can use to help connect to the 9 days:
(1) First, we spoke about what the Beis Hamikdash was
(2) Then, we spoke about how life is different now that we don’t have it. And why that’s sad or difficult.
(3) Lastly, we started coming up with ideas of how we could help “rebuild” the Temple with our actions (e.g. sharing, forgiving people, being kind, recognizing G-d in the world around us, etc.)
We all walked away with some plan of how we could be better and help “build a space” for G-d in our home.
Hope this idea helps!