It is now your duty to inform your parents that the practice of liturgical dance is not only banned in the US but also renders the Mass they attend, illicit. I battled this with the pastor of my (former) RC parish and won - but only by making the time to address the issue with him. When that could not be resolved, I wrote to the diocese which, no surprise, supported the pastor. Undaunted, I quoted from the documents posted in the link at #5, summarizing with the statement that "all Catholics are entitled to a valid liturgy". That was it! They could not refute those documents.
The only way to stop this practice is to address the issue directly with the pastor and, if necessary, the diocesan Director for Divine Worship. Are your parents up to this? If not, can you do it for them? Should the letter writing campaign fail, send copies of ALL correspondence to Francis Cardinal Arinze, at the address posted in link #5. This is your Mass and you and your parents, are entitled to a valid liturgy.
We're on it, don't worry. My parents are not up to the fight. Their parish has been hijacked by Episcopalian converts who are far from orthodox Catholics. They have started attending another church in the vicinity that is uber-orthodox. They are all fought out and the pastor basically tells people that are towing the Vatican line to back off. They have asked that my husband and I file the complaint instead of them. My husband, who is a convert, is WAY offended by what he saw. We do have an office of divine liturgy in Atlanta. They will be hearing from us.
Thanks again for your post. I love my Catholic brethren at Free Republic. What a fount of information y'all are!