Hi Angie!
I love the idea of including significant, non related people in the family tree.
I'm happy to see many schools changing the way they do this common project. I think it's great when teachers make the family tree project with your point in mind.
It helps so much to talk about all of the different types of families, and all of the different types of family trees out there.
One teacher I know created a family forest project. The child's tree was in the middle of the page. Each child could include as many additional trees as they wanted, with each tree representing someone special or important to the child.
One child even included Santa Claus and the Tooth Fairy, lol!