Followup: Whew, that was fun!
The controller has a new "mouse" mode, which I found very smooth and intuitive. The new Mario Party mouse-only minigames were a blast: classic Mario Party shenanigans.
Also did Mario Party with the camera/microphone addon, and that was perhaps a bit gimmicky but still a joy.
The highlight of the event was 24-player Mario Kart knockout (the last-placed racers get removed each lap).
Also, the event had close to 50-50 male-female attendance, which was great to see.