If I were his family I'd be shitting bricks. Talk about having a huge target put on your back all of a sudden.
Hate to tell you, but the football is useless without the nuclear codes that the president carries on his person at all times. Exactly why would his family be targets if he doesn't have the codes? And you also have to consider the fact that he is next to the president almost all of the time, which means that in addition to protecting Trump, the SS is also looking out for him to a certain degree.
Because they could be kidnapped and he could be faced with the ethical decision of doing something to disarm or hurt the football that could cause it not to be useful during a nuclear attack, to the point that even if he were there with Trump, Trump couldn't use it.
Are you serious? Are you that simple?