Every year, my school has "Grandparents' Day", when grandparents can come to school for the afternoon. This time is filled with special activities put on by the classroom teachers, and our school librarian holds a book fair the same week. The students who are scheduled to come to art during Grandparents' Day come anyway, and bring their grandparents! I'm sure you can imagine the chaos of having more than twice my normal class size crammed in my small room! Thankfully, the grandparents are very well-behaved, and encourage good behavior from the kids :).
This year, we looked at Picasso's Hands with Bouquet, and made our own version. The grandparent traced the child's hand, and the child traced the grandparent's hand so it looked like the child was giving a bouquet to their grandparent. A few students had no grandparent with them, but many of the students had 2 grandparents, and were willing to share.
We also had a wonderful aesthetics discussion about Picasso's artwork. The grandparents chimed in briefly, but the students were able to guess the meaning of Picasso's picture on their own: friendship. Below is Picasso's picture, followed by some photos of the students working with their grandparents, and a few finished drawings. I did this lesson with 1st grade and 2nd grade.