You might just have to accept that he is just not interested in going out and about like your other pups. When you have people over it is probably important that he have a “safe place” where guest will not bother him while they are at your house. Does he love to do tricks or agility? Those can be confident builders for some dogs but others would just like to stay behind the scene.
I would just try to create the world that he is most comfortable in. If he does not like the expo I would not take him, but try to do what he loves.
You know your dogs better than anyone and can read their mods and likes, and it sounds like he is just different than your others.
They are all so cute, of course
