I knew my drinking partner would go down the wine route...hehe!
My suggestion depends on whether you reckon your client is into Turkey for Christmas or not!
One of my 3rd party contractors buys us our turkey every year for Christmas... there's 20 people in my project team so it's quite a few turkeys! But it's a nice touch as you don't have to worry about getting the turkey for Chrimbo!
They send a couple of lads to an amazing organic farm in Lincolnshire and pick up 20 fresh organic free-range turkeys, each weighing around 17-20lb from memory - more turkey than you can shake a stick at, and worth quite a bit if you had to buy them in the shop!
Another 3rd party contractor buys us all our tipple of choice... so for me that's either a vintage port or some top notch red wine... can't beat Chatteauneuf du pape for Christmas baby! Woot!
So a few ideas... hope that helps!