At that time I didn't realize that in our small town what is said to one person is said to all. I was a city girl with no experience with small towns gossip.
I'd say that same rule would apply to people hearing about a relative and her son burying themselves in their cell phones during a family holiday. So, getting back to the original question, yes, I would say it is rude. It is something that will be seen by many people as making a statement that you are too good for them or are rejecting their company. That may be a statement you are okay with making, but I would assume that "my sister/cousin/daughter in law and her son were so rude burying themselves in their cell phones one of the only times we see them" is something that may well be said and repeated.
