Well it depends really.
If you're "rairly, rairly" posh, and have a hice with 234 bedrooms, and plan to send your son to Eton, and mix with people who have children called Tarquin and Jacinta and who say "ears" instead of "yes", then go ahead. Little Percy will fit in beautifully.
If however you are a normal person who plans to mix with normal people/children, then calling the poor little sod Percy is condemning him to a lifetime of misery and having his head flushed down the toilet.
HTH.