Had to change our trip to Argentina to May. Want to definitely go to Iguazu falls, but will stay only one night. After that, since we have extra days besides the 5 days we will be in Buenos Aires have many ideas for one more stop, but don't know what makes the most sense. Either going to Salta, Mendoza or Patagonia. Obviously, we can't do everything, but it's my daughters first trip to Argentina and want her to have a great time.
If there is a nice Estancia in any of these places please let me know -

we loved our few days in mendoza...in fact it was a highlight of our time in SA....its a bit costly to fly there but the overnite bus is comfortable---the ultra lux bus...

Ith 6 days accounted for it seems you have around 8 to play with. A bit more info would help e.g.What are your specific interests? Food, wine, scenery, nice hotels activity?

My favourite place in Argentina was the NW area around Salta. A 4/5 day drive around the region would allow you to pass through some of the most amazing scenery in South America. Good food, wine and places to stay along the way. Plus, you would have a few days left to visit somewhere else.

Patagonia ia also very beautiful lots of lakes, glaciers and mountains but I am not sure if May is the best time weather wise.

Mendoza is good for food, wine and is home to some really great hotels but it was my least favourite of the places we visited in Argentina.

May IS a bad time to visit our South.

I vote for the NW area also! Good wines, great food, nice hotels and the most amazing sceneries! All your expectations will be fulfilled! I also made alot of efforts in convincing Crellston, now he wants to come back and stay! ;o)))
If you need more info about this area, plas, do not hesitate in making all the questions you consider necessary!
flitnatones