SAFalconer,
I have hunted nearly all of the provinces in RSA, and in my opinion, the Limpopo Province offers the greatest variety of huntable species. You can encounter up to 40 different species on some properties not including the many small predators, varmints, and upland birds that you mentioned....I also feel the trophy quality is the best in the Limpopo.
As far as the upland birds, I would do some inquiring with each of the outfitters you may be considering, as some have property more attractive with cover and available feed than others. Some outfitters plant fields specifically to attract and hold birds. They also maintain the preferred cover. Bird hunting is one of my favorite things to do during a safari. On the right property, it's possible shoot through a case of shells in a morning session.
Please feel free to PM me if you have any other questions.