Thanks everyone for your help.
I think we're going to try and do 3-4 days in Calafate / Chalten; 4-5 days in BA; and 2 days (1 night) in Iguazu.
We're going to go straight from BA to Calafate -- seems to be the best way. Can anyone recommend a travel agent / tour guide / company in Calafate Chalten that leads a short (2-3) trek/hike? I've found a lot of info about daylong excursions and 2-week trips, but nothing in the middle.
Thanks.