I have nothing against people who enjoy watching sports, but it seems strange to me to consider sports viewing as inherently virtuous. You could be doing anything with a computer and a network connection. Even watching sports.
Having been taken to professional and high-level college sports many times in my childhood, starting with an NFL game as a toddler, I'm not saddened by it: until I was a teenager, most of the games were either overwhelmingly far out tediously slow, and in either case only weakly engaging. But my being there meant my parents could be there and I could be with them; I invariably had something else to engage me; I never regretted it and I don't think my parents did either.
Try this simple modification to get them on your side of the argument:
> I remember being at a TED Talk where a kid was immersed in his device the entire night, despite being in a $148 seat to (IMHO) the most attention-maintaining of all events. Having never been taken to a major thought leader event for my entire childhood, seeing this saddened me.
I remember being at an NHL game where a kid was immersed in his device the entire night, despite being in a $148 seat to (IMHO) the most attention-maintaining of all sports. Having never been taken to a major league sporting event for my entire childhood, seeing this saddened me.