40 years + 8 kids + 17 grandchildren (so far) later:
They were surprised. And even more surprised when they were supposed to dance to "their" song (Cherish by The Association) and the DJ mistakenly played Cherish the Love by Kool and the Gang. My parents were confused because the DJ announced the song was specially picked by the children.
We were laughing so hard but had to wait until the end of the song to explain it to our parents.
Floor dancing ... or break dancing (?). I call it floor cleaning, which results in children cleaning.