This is one of my kid's favorite Christmas activities every single year. Since I do not let them help decorate our main tree in the living room (go on and judge, I know all of you are*) they love going to Grandpa's and helping him to decorate their tree. They have a great family tree with a great mix of homemade ornaments, colored and white lights, expensive crystal decorations, and regular old balls. It is the kind of tree that I grew up with . We all got together usually for a Family Home Evening and decorated it. My kids love that! And because my dad lets them help him out with the decorating I do not feel bad not letting them touch my tree :)
*In my defense we do have a second tree that I will allow them to decorate if and when we ever get the basement finished and have a family room again. I am happy for them to have a fun kid tree that they can design and decorate.