I would say, "¿Dónde está _____?(either one of the family members or a body part). The boys would take turns finding that object. Once they found it they had to say, "__________ está(n) en _______ (shape) _________ (color)." For example: "¿Dónde están los abuelos?" "Los abuelos están en el óvalo azul."
It only took them a couple of times practicing before they could say the sentence without help. It ended up being, not only a great way to review previous vocab (family, body parts, shapes, colors), but also to practice grammar and speaking.