Seems Doxie is seeing any visitor as an intruder or threat upon her territory. Kids are always confusing for young dogs due to their spontaneous nature, along with the noise.

You might want to keep the puppy on a leash until she stops barking and calms down. In another words get past the first 5 minutes in a controlled manner.

Also to consider is socialization outside of her own territory with people. That might take her out of a territorial defensive mode.