'70 or '80s Movie about Orphans and a Grandpa?

I remember seeing this move back in the 80s but it looked older than that. It was a TV movie I believe about an orphan boy who is taken from his grandfather (who is in a wheelchair) and is locked in a room with glass bottles. The foster parents referred to him as "orphan child #2" next to him is a girl who ironically he knows from school. Other things I remember are both of the kids going out for Halloween as ghosts with "1" and "2" on their sheets and the grandfather building a parade float to disguise himself in order to get his grandson back. Thanks for any help!