Chain select queries within an eager load?

How can I chain 2 or more select tags within an eager load? I am using select because I only want to load these 2 columns, nothing else. Tried many things.

    $teams = Team::with(['captain' => function($q) {
        $q->select('id', 'name')->where('show_name', true);
        $q->select('id', 'username')->where('show_username', true);
    }])

Obviously this first implementation will not work, but it shows what I am trying to achieve

        $q->select('id', 'name', 'username')
          ->where('show_name', true)
          ->orWhere('show_username', true);
    }])

This second implementation returns both 'name' and 'username' if either show_name or show_username is true. I wan't something like

        $q->select('id', 'name')
          ->where('show_name', true)
          ->orWhere() // ??
          ->select('id', 'username')
          ->where('show_username', true);
    }])

Thanks

via Chebli Mohamed