Thanks for the feedback.
I think we are looking at just a day trip to the Argentinian side. The flights seem very reasonable online for early am departure and evening return.
Can we safely do this on our own? Such as finding a taxi around 4am from the Sheraton to take us to the airport? Taxi from IGR to the Falls, etc. Are the flights reliable? Can we see all we need to see, do the boat ride to the falls, etc without a guide?