
Hi
I don't think you have quite thought through the implications here, in the nicest possible way. No reputable breeder will sell you a puppy unless they have met the ENTIRE family, as they will want to meet everyone and see how they interact with the dogs and puppies, so a surprise for the kids isn't a good idea and unlikely to work. Also Christmas isn't a good idea not just for the reason of people giving puppies as unwanted presents, but because it is a very hectic time of year with plenty of visitors, things going on etc, and it isn't a good time for a new puppy to arrive in a household as he will need peace and quiet to be able to settle in well. Then there is the question of house training -this will be a LOT harder during the winter than during the spring/summer, as you will have to take the pup out many, many times a day and wait for him to go, and believe me, in the dark,cold and wet it isn't very nice. :) Therefore whenever possible most breeders will try to have pups for the spring/summer. Not always practically possible of course, but really it does make life a lot easier.
You can find reputable breeders by contacting the Golden Retriever Culb. Their website is:
http://www.thegoldenretrieverclub.co.uk/ Make sure you ask about the parents' hip scores, elbow scores and eye testing.