I love response that you got from Valerie S. I could say what she told you, plus perhaps that I do understand your son very well, even though I am waaay older. When I got engaged to my husband he was a very popular bachelor, never even engaged before, he was 44 and I was a European doctor who "managed" to "get" him. His friends and family (lots of lots of them....) were all very curious about me and all wanted to talk to me, and all were asking same basic questions that I had to respond to over and over again. They were nice, but all I wanted is for them to leave me alone finally. And I had to use all my adult strength and experience to remain nice and polite. I hated it after a while and dreaded all those gatherings.
I noticed that adults tend to pay a lot of attention to children and ask questions like "oh, and how old are you", "do you have any brothers or sisters?" "what did you get for Christmas"' "did Santa come to you", "is this thumb good" "are you shy?" etc. For crying out loud, sometimes when I hear people saying all these things to my daughter(especially the "thumb" thing, how rude!!!) I feel like saying "back off, leave her alone, or she will feel like an animal in the Zoo". We are adults, we should know better than that! I would say be with him, protect him, don't say "he is shy" in front of him, or even say something that shows you are proud of him, smile beautifully to cover his grumping and go on. He will outgrow it, get used to it or just learn to deal with it. With time he will be getting less and less attention and it will make it easier.
Good luck and say hello to your son from me (lol).