https://www.youtube.com/watch?v=wTvRNwslYxA&list=OLAK5uy_kK0U26G1M2NCWwY_0O1-dF_qGAajhgnbc&index=9
I did this last year with my Year 6 leavers.
They just sat in a formation and stood when it was their part to sing. Really simple but really effective and the parents had to listen to the lyrics.