Visiting non-religious parents on Shabbat

Q: Should I go to visit my parents on Shabbat even though they do not observe Shabbat?
A: There is no law that one is obligated to visit his parents. It is a kindness and as in every kindness, it is according to one's ability and the need. It is possible that your parents really need it: they are sick, lonely, etc… And according to your ability – this is a technical question: is it far or near? Do you have a car or time? And it is an emotional question: it is pleasant or difficult there? As a result, you do not have to go every Shabbat, this is extreme. And never going for Shabbat is also extreme. It is based on your ability and their need. It is not easy to quantify: perhaps once a month.
Q: What should I do when they watch TV and the phone rings?
A: Do not watch the TV and do not answer the phone.