Thank you both! I know, Christmas is probably not ideal....but, if we are spending that much money on a dog it really will be one of VERY few gifts she will get for Christmas! But you have given me some food for thought....
Getting a puppy at Christmas is a bad, bad BAD idea!!! I would explain that to to your daughter. Certainly at 10, she should be able to understand, that the puppy will BE her main Christmas present, but it is best for the puppy to get him or her when the PUPPY is ready, and not at Christmas. Better to get an early Christmas present than to wait for a promised puppy from a later litter!
For Christmas, itself, you can give her things like a pretty harness and leash, or other fun accessories. (there are LOTS needed during the first year!!!)
As others have said, you will miss out on socializing and bonding with the puppy appropriately by waiting till 4 months. It will also be a very late start on puppy kindergarten, which is vitally important. It will also, potentially, make potty training a lot harder, depending on what the breeder does in the mean time.
Havanese are probably one of the quietest, best-tempered of the small breeds, but ALL puppies do some barking. They need to be taught when it is appropriate and when to stop. If you lived through a JRT as a puppy, (even if it was long ago!) you will have NO problem with a Havanese puppy!
I think Jr. handling is a WONDERFUL way for your daughter to enjoy structured training time with her pup, especially if the breeder is willing to mentor her!