Are you at all crafty... You could get a large sheet of butchers paper and draw your own tree.. Or have kids and family members help to draw the tree you imagine and everyone can do their own branches or leaves as a family project. It may not be as Picture perfect but homemade has its own charm sometimes.
A family that would look like a tree would be a family of stick bugs.
....all family trees?....just think, you start with you and your siblings, go up one to your parents and your siblings spouses parents, then to their parents and spous's parents etc....it gets pretty big pretty quickly=)