I found the answer online- the normal size of appendix ranges between 2-20 cm  but a normal size is 6 CM. So if a child of 7 has an appendix in the range of 2-6 cm that is normal. 

Note- I am not an expert on such matters!

I am not a doctor so I can't opine according to medical books.  What I can say is that I was operated upon due to appendix as well as some family members also had undergone surgery for the same. I have no idea regarding the length size but it is very problematic if gets infected. Sometimes appendix gets twisted and stretched, and even moves towards the back which is not a very healthy sign. We usually know that appendix bursts so even any small problem should not be ignored. 

I am no expert but size of appendix is not as significant as the actual condition of it. About a centimetre and a half less or more than normal is okay, but it should have no inflammation or signs of sepsis. As appendix is the only organ in human body which has absolutely no function of any kind, removing it with surgery does not have any later effects or anything. Why are you asking whether surgery is an option because it is a bit smaller than normal?

Because one kids of my colleague is passing from pain of appendix now pain is under control but she got pain attack every month once a while so that I am raising question here to get more opinion.

Then the best thing is to get it removed than take a risk of getting it bursted any time.