Suggested steps:

1) Go to: http://tinyurl.com/nw9f4

2) Then type "Isabel" in their search feature.

3) Draw your own conclusions.

Have a great time in our country with your father and DH.

You can certainly plan a visit to Iguazu on your own. I would suggest flying, and you can buy your tickets online. I stayed at the Pension la Sorgente and liked it, but there is also a pricey Sheraton actually in the National Park. You don't need a guide for the falls, you just follow the trails. If you don't stay in the park there are buses that go directly there.

I recommend seeing both sides, but I don't know your nationality WRT visa requirements for Brazil.

Another option from BsAs is the ferry to Colonia or Montevideo.

While the Sheraton is more expensive than other hotels, it is the only one inside the national park. You can't beat it for convenience. Some prefer falls view rooms, but If we ever return, we would opt for a cheaper, jungle view room. The reason is that you are not in your room enough hours to really benefit from the great view. In addition, the restaurant downstairs (where you have your free breakfast) has large picture windows with a magnificent view - at no cost whatsoever.

I recommend two nights at Iguazú. It is truly awe inspiring.

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Vic's travels: http://my.flightmemory.com/vogilvie

I've been up to Iguazu twice for 2 night stays and loved it. I stay at the Orquideas Palace, which is about 1/2 way between town and the park. The local bus stops in front for easy access. Your dad should have no problem with the walkways, but if he does, there are golf carts which might help him on some of the pathways.

I've only been on the Argentine side as I thought the price for the Brazilian visa was too much for a daytrip.

Do make sure your dad is very careful of the sidewalks in Buenos Aires - they can be a nightmare for someone with balance issues with many holes and missing grates.

Just visited Iguazú three days ago. Did both sides with the Brasilian side first. (Already had a Brasilian visa.) Took the Cataratas bus from the central bus terminal. $60ARS round trip. Sorry to say that I was under-whelmed. Diddo for the Bird Park.
Disappointed that inclement weather prevented us from experiencing the Paseo de Luna Llena (Full moon walk). Check the full moon calendar dates against your travel plans. There are only four or five days a month that the park is open at night.
However, the Argentian side was glorious! There is a LOT of walking and if the heat and humidity are oppressive (probably will be) it could prove to be difficult for your Father.
Unless you take a private tour (unnecessary), you will need to "keep up" with the group and that may mean moving through the park at a pretty good clip. That being said, I was on a group tour, Aguas Grandes Tours with guide Junior Cesar Rodriguez. He easily went back and forth between Spanish and English. Junior was very accommodating with questions from the group...lots of history which I enjoyed.
Had no problem with insects during my two days. Bring sunblock, sunglasses, water, hat and consider having something with long sleeves (not tight). I am fair skinned of Irish descent and found the sun to be too much. My travel companion couldn't get enough sun. Food is no problem as there are many concessions.
Enjoy your time at this magical place.
Do consider the day trip to Colonia del Sacramento, UR from Buenos Aires. Had Beatrix Rivas (099 521 060) give us a tour and she was wonderful. Someone from the Visitors' Center can call her upon your arrival on the ferry. Buy your ferry tickets online from SeaCat Colonia or call them when you arrive in BsAs for a fraction of the price from Buquebus. Everyone travels on the same boat anyway.

We are booked on the same cruise and also have booked the 4 day Viatour bus tour to Igauza.. However, because of the Brazilian visa requirements we are probably going to cancel. Now we are scrambling and looking for an alternative..such as the possibility of doing the Viator and skipping the Brazilian side of the falls.or doing it independently.
Hopefully, we will meet on the cruise. If you come up with any concrete ideas for the Igauza Falls trip, please consider sharing them. Bon voyage.

Click on my name for my TR for a possible way to see the Brazilian side without a visa. Likely only for independent travelers, though.

Thank you all for your replies. I have been so busy with Christmas that it is only now that I am reading the last replies.

We have booked a flight from BsAs to the falls. We are booked at the Sheraton since my dad may not want to do much walking he can still enjoy the falls from the hotel. Since we had planed to stay in BsAs for a week after the cruise we are going to the falls February 5-7. The Sheraton was booked earlier in the week so that is why we will go just before we fly home from BsAs.

Bourlamaque, are you on the roll call through Cruise Critic? If not, it is a great tool to hook up with people. There will be a "Meet and Greet" which will give people a chance to meet at the beginning of the cruise.

Just wanted to give an update. We LOVED Iguazu Falls! We had the best weather. No problems with bugs either. We stayed at the Sheraton and loved being right in the park. It was so worth it. We took the boat ride that takes you right up to the falls. You get drenched but it was so fun. My dad loved it! Lots of stairs to walk up and down to do the boat ride but he did it. We bought the video afterwards and love reliving the experience! Highly recommend going to Iguazu Falls. It was breathtaking!

Thanks for reporting back. Glad you had a good time - although i can't imagine NOT enjoying the falls.

Well done, Terry - good planning and good weather - great combination to enjoy your visit to this incredible site; not impossible for any age or most situations. Thank you for posting back.