I'll join you in saying it is annoying. It is a bit different in my ward - the parent goes up and ends up whispering what to say in the kids ear. The kid really has no idea what they are doing or what a testimony really means. On the other hand some of the most sincere, sweet testimonies I have heard have been from an 11 year old. I actually found an article on the Church web site saying kids should be encouraged to bear their testimony in primary and at home.