Hi Robette,
Sounds like a great trip. As far as I know your options for Salta to BA are pretty much:
- Direct flight (2 hrs)
- Bus (22 hrs, and not much less expensive)
- Various indirect flights that will cost more and take at least 2 hrs to get to (Jujuy, Catamarca, Santiago del Estero...)
- Teleporting (not yet available, but one can always dream)
All in all, especially with the kids in mind, I would think your best bet is to bite the bullet and take the Salta-BA flight.
Either way, have a great trip!