Neil Gaiman's Blueberry Girl Poem is absolutely ideal for a non-religious naming ceremony (and is available as a beautifully illustrated book too which is a perfect present for the occasion). - but you say "Christened" - aren't those usually religious??
Thanks for your responses! It is a christening and will have a religious reading but we're able to chose a non religious one too. I'll have a look at blueberry girl now... I would love guess how much i love you but husband isn't too sure!