Like any other group of people dedicated to a beleif system, in the Jehovahs Witnesses, you will find those who are well adjusted and happy. What you won't find with just a glance however, is the sublayer of misery and dejection that accompanys the purview of many in the religion who don't embrace their beliefs wholeheartedly. The resulting depression has decimated many children who might otherwise have grown up with dreams and desires relatively normal and intact.
You 'see' a child who simply wants to join in but won't because they feel strongly about their beliefs. I hate to burst your rose colored bubble, but thats putting things a wee bit too lightly. Children of jws wrestle with huge ethical issues regarding whats 'proper' that are far beyond their emotional capacity to understand. On one hand they feel compelled to join in on the simple fun that should be a part of growing up but on the other, they are being told its not right to do so. What you might not be aware of are the reasons given to those children. They are told that the celebrations we normally endorse, are pagan. They teach their youngsters that these celebrations are the instrument of Satan and that only Satans followers would take part in such things. YES, this means that you and all of his little schoolmates are all part of Satans world.
Furthermore, all of those, of Satans world, will die, VERY SOON, in an Armageddon that will re-establish Jehovahs rule in an earthly paradise. The children are taught about how the crows will strip the meat from the bones of those destroyed by Jehovah, about how they will be able to join in on the uplifting work of disposing of all the bodies of the wicked ones in the new system. These wicked ones, are you, and all his classmates. This same motivation is used to control the behviour of every JW and they start it in the cradle. The JW's are one of the most clever insidious cults to ever be recognized as a piece of Christianity to ever come down the pipe.
That little kid you see, who you think is simply choosing to NOT celebrate...theres a lot more at work there than you may have the capacity or desire to believe. Those well adjusted ones? Yup, well adjusted, they are completely at peace with the fact that you, and their classmates will soon be dead. Its the well adjusted ones that are the scariest, because for them, the mind control dementia is complete and for them, their may be no hope of ever living a normal life.