Ok, honest horrible answer. If it was me and I wanted to get a dog, then this is not how I would do it, especially with children in the mix. I would be going to a well run rescue that assesses the dogs in its care and will also assess you and your children and make sure that your choice of dog matches well with what you can manage. I would also think VERY hard before getting a dog so near to christmas. Any dog needs a calm quiet introduction to a new home and I am betting that calm and quiet won't describe your house at christmas.
I think that getting an older dog could be a good idea for you. Pups are lovely to have but blooming hard work especially with children, especially with a 3 year old. You will still be rescuing a dog if that is important to you.
Honestly I think this girl has got you by the heartstrings. I think that this decision is one that needs to be made firmly with your head for everyone's sake, including the dog you rehome. Sorry but I do.