The point is, a dog is a LOT of work. So if she's only getting it "for the kids", it's not likely to work out. SHE needs to want the dog, and be willing to do all the work (because Mom always does all the work, no matter what she tells everybody). If she's up for that, I actually recommend an adult dog from a good home. Puppies need so much training and attention. An adult dog that's already trained would be a lot easier.
Very small dogs aren't usually great with kids. They tend to be defensive since they're so small, they feel insecure around people they think might be rough with them. Kids do have a tendency to be careless around dogs, and I've known several small dogs that were accidentally hurt by the kids in the home. A larger, sturdier dog tends to do better with kids, but a larger dog also means a larger feed bill, larger poop to clean up, and a lot more shedding. Plus a lot of the good family dogs are sporting breeds, who tend to be INCREDIBLY hyper as puppies. So it all depends what your sister really wants in a dog.
For the record, I DO NOT think that getting 2 puppies would be a good idea, and Basenji and Shiba Inu would not be breeds I'd recommend with little kids (sorry, isyssot_7399!).