Until I read your comment about "small but not too small", I was going to suggest a Maltese. They are tiny, usually less than 4 kilos, but they do not shed, are great with other pets, are okay with kids, and are a lazy dog breed that will probably do a lot of sleeping when you are gone for those long days.
They can be kind of fragile since they are so small but your kids are old enough to not be too rambunctious. I would not want a Maltese to have to worry around a clumsy toddler.
If the Maltese is too small, the French Bulldog is a larger and a lot sturdier. He does shed though so if this is an important point you may not want that kind of dog.
Personally, I think you would be better off with a Maltese.