Upvote:9
Signing a passport is a requirement for each new passport. As much as anything else your signature acknowledges that you have read its terms and conditions, and that you took possession of it.
There is no requirement that signatures remain consistent throughout a person's life time. In your specific case, there would be thousands of applicants in a similar situation. Not just children, but older folks also whose signature changes. The examiner who processes your application will have seen the same situation countless times.