While the hamptons carryall in all sizes is a lovely bag, as are satchels, keep in mind we are not just recommending something for a working woman, we are recommending something for a busy mommy, and I find those bags to be a PITA for me...and I don't even have kids yet.
The ergo hobos are the best bet I think because they do NOT come off the shoulder, very low maintenance and look classy OR casual if you want them to.
I vote the large belted hobo in black. You really can't go wrong and she will get many years of use out of it as well as many compliments. The leather is sturdy and beautiful and the belted detail adds something special.
The hamptons carryall is much harder to maintain in terms of keeping it on your shoulder.
The chelsea turnlock pictured above doesn't present me with any issues...I have the wristlet and it's very easy to turn it and open, better than a zipper. The ergo hobo has a zipper but it's big so it doesn't really have any problems there.