I can see the point if you have a child that is particularly vurnerable and has other health problems. In those circumstances, you might want to be careful about them getting something else. At the end of the day, we all need to catch those childhood things to build up immunity as adults.
With it being only a few days to Christmas, I would prefer my kids noy to catch anything now and spoil their Christmas a bit. We have had them ill on Christmas day and that is a bit of a shame. However, I have never avoided anything with my kids and they are remarkably healthy. My eldest is 9 and hasn't missed any school days for 2 and a half years. My younger son is not quite so great, but he has only had 2 days off over the same time period. I think some of that will be down to being a working mother though. We tend to send the kids to school and hope for the best rather than keep them off to see how they are! As for avoiding friends and family if they are ill, that seems way over the top to me. Normal day to day measures such as washing your hands properly, using tissues and disposing off them properly are all that is required.