My 4-year-old son is not fully engaged when he has a friend over for a play date. His twin sister makes friends easily, and the difference between them is glaring. When I arrange a play date for him, he is excited, but then, after the friend arrives, he gradually slips off to play by himself.
Afterward, he will tell me he really didn't have a good time. Do you have any suggestions as to how I can help him become more social? I don't want him to become a loner.
The Serenity Prayer says, "Change those things you can change and accept those things you cannot change."
You're describing one of your son's personality traits. Social reticence may in fact be the defining feature of his personality. Some people, from the get-go, are outgoing, gregarious, highly social. Others are socially reserved, introverted. As with your twins, personality differences of this sort are often evident from early on (even in identical twins).
Over the past 30 years, a lot has been made of the need to respect "individual differences" in children, but the fact is we are becoming less and less tolerant of childhood behavior patterns that fall even slightly outside a narrow (and ever-narrowing) definition of what constitutes "normal."
A good example of this is found in schools where, on the one hand, teachers are encouraged to respect and accommodate individual learning styles, while on the other hand, they are told children with different learning styles may have disabilities that require professional help.
Likewise, many of today's parents - especially the more well-educated ones (who tend to read entirely too much of the prevailing parent-babble) - worry about any behaviors that don't fit the proverbial mold. They suffer from Too Much Information Syndrome, a peculiar brain malady characterized by over-sensitivity to anything that seems even the slightest bit "off."
This is exacerbated by the fact that today's parents seem to think their job is to make sure their children reach adulthood without any emotional baggage. That's an impossible dream, of course. If you are a person, then you have personal problems.
Correcting a behavior problem (for example, disobedience) does not require the child's permission, but the only person who can overcome a personal challenge imposed by the birthright of personality (for instance, shyness) is the person so challenged. That requires knowing the trait in question is problematic and making a conscious decision to overcome its limitations. A child of 4 is not capable of anywhere near that degree of intellectual and emotional maturity.
When your son is older, perhaps he will see the wisdom of making more of an effort to connect with people. In the meantime, his social difficulties are just something he and you are going to have to accept and live with.
You can encourage him to reach out to other children (which, I take it, you already are doing). When you see him pulling away from other kids, you can suggest a game they can play together. The best thing you can do for him, however, is to relax. Introversion isn't life-threatening. Furthermore, most child-introverts are no longer introverts by the time they are in their thirties.
In short, your best course of action is to stop trying to solve this problem for your son. This ball needs to be in his court and his alone. The more you try to bounce his ball, the more likely it is your good intentions will prevent him from learning to bounce it himself.
We would do well to recall what people once said about such personality differences: It takes all kinds to make the world go 'round.