I saw Barron smiling on TV once.
It was during the inaugural parade, on January 20, 2017.
Barron was waving and smiling at some men who were driving tractors past the presidential reviewing stand.
Other than that, I don’t recall seeing many pictures of him, smiling or not. Melania has been very protective of her son, and with the barracudas in the media, who can blame her.
The photographer controls the button and decides what you will see. I’ll bet Barron smiles frequently and photographers spent hours waiting for the smileless shot.