What a sweet mommy you must be. How loving it is that you desire that your son have the experience of new friendships. I am especially uplifted by your attitude that seeks to appreciate his unique method of finding his comfort in new situations. I am under the belief that if we do not unduly push our children they will indeed find their way and blossom as out going and friendly people. I have proof of that within my own children. When my sons were young they were very much like you describe your little boy. In fact one of them could hardly be out of my sight. Now that 'little' boy is living in New York City and is pursuing a PhD in Mathematics and will be married in June. He has traveled the world and finds that there are amazing and interesting people and adventures in every part of it.
The words quiet and shy should not be confused as meaning the same thing. They do not. A quiet person is just that. It is their personality to sit back and observe, listen and be attentive before they join into a group. The way your son behaved during his first experience with story hour is certainly in character with a quiet personality. Shy on the other hand can mean anything from a refusal to speak to people or an actual fear of being with people. To be shy means something totally different than being quiet by nature. I think that your son's response at the story hour is healthy and certainly his personality and as such will serve him well as he matures. It is always best to 'size up' a situation before you jump right in with both feet. My husband is very quiet by nature yet he is not at all shy. I do have a daughter that is a bit shy. She does not like to be with people as much as most teens and sometimes seems to prefer to avoid situations that will require her joining into a group activity. She works to overcome this shy feeling through theater and 4H. She is overjoyed when she is able to give a speech without trembling. hee, hee
Your son is quite young and still probably finds the companionship of mommy as his most favorite activity. Your are probably his best playmate right now. Gradually he will gravitate towards other children who share his quiet nature. Yet do not be surprised if more gregarious children seek him out. His quiet calm nature will be soothing for such children. They will find that he is a wonderful listener and will appreciate him all the more.
Look for activities that bring out the best in him. Pray for guidance and direction to such activities. Jesus was a sociable person and it is in our nature to need the company of others. It is far better to have two friends who appreciate you and understand you than to have several who you feel stress you to be something you can not be.
Thank you for taking the time to write. Let us offer up a Hail Mary for the needs of mothers who are struggling to find friendships despite the isolation of homeschooling and mothering.
Sending out a prayer,