Three days - not much. Here's some options:
Option 1
Friday - morning flight to Calafate - visit Perito Moreno in the afternoon - overnight Calafate
Saturday - morning bus to El Chalten - afternoon hike to Cerro Torre
Sunday - morning hike to Fitz Roy look out
- bus back to Calafate - flight home
Alternative to above is to stay in Calafate region and stay on an Estancia and do some horseback riding. Another alternative is to stay in Calafate and do a glacier cruise, a glacier hike, or some 6WD adventures.
Option 2
Friday - fly to Bariloche - drive to San Martin de los Andes - explore
Sat, Sun - hike, boat, mountain bike, etc. fly back Sunday night from San Martin or Bariloche
Option 3
Friday - Morning flight to Trelew - drive to Punta Tombo to visit the penguins then drive back to Puerto Madryn and stay the night
Saturday - slowly drive up the coast looking for whales, and then go to Puerto Piramedes and do a whale watching trip. In the afternoon, drive to Punto Delgado to see the elephant seals. If its in your budget, stay at Faro Delgado right there
Sunday - explore the eastern coast of Peninsual Valdes and then drive back to Trelew in time for a flight back to BA
Option 4
Friday - fly to Ushuaia - explore
Sat - full day explore
Sun - morning explore - evening fly back to BA