iguasso falls

Where exactly are you arriving? IGU airport in Brazil? (There is no Iguassu. In Portuguese, the Brazilian town is called Foz do Iguacu--FAWS doo eee gwah SUE--, the airport IGU, and the falls are referred to locally as the "cataratas"--like the word cataracts. The Argentine town is Puerto Iguazu----pooh air too-eee gwah ZOO, and the airport is IGR.)
IMO, a tour of the Brazilian side of the park is not necessary. You can easily take the local bus (about R$2) from IGU airport to the park entrance, leave your luggage in the lockers at the entrance, and walk the asphalt path on your own, stopping to take photos. It should take about 3 hours or so, and IMO does not require a dedicated guide for overthought explanations of falling water and furry coatis. If you have time, see the interesting Bird Park just outside the park entrance (maybe another couple of hours),
Then get another local bus or a taxi across the border to Puerto Iguazu, Argentina, to enjoy that side of the park.

Like said above, you don't need a guide to walk around the park looking at the waterfalls.
On the Argentinian side, where the main part of the waterfalls is, you can go on a boat ride to come close to the falls.

ok, I thought it might be easier to arrange airport pick up and then falls and then drop off at our hotel. we have less than 24 hours, we arrive at 12:00 pm and leave the next morning at 11:30 am.

Where is your hotel?
Where are you leaving from?

we arrive at 12 pm at IGU and we are staying at the Sheraton in Puerto Iguazu. and we fly out of Puerto Iguazu at 11:30 am the next day

What is 12 pm - is it noon?
If your time is limited then proceed directly to the Argentinian side - that's where the main spectacle that you want to see is. You won't have any time for the waterfalls the day you'll be leaving from Puerto Iguazu.

ok. thank you for the recommendation. yes pm (post meridian) is noon. so perhaps we'll just go straight to argentinian side... we'll be happy seeing what we can, this is just a little bonus side trip between Rio (4 nights) and Buenos Aires (4 nights).

If it is still possible to change your flight out, book one later in the afternoon to be able to see a bit of both sides. IMO it's hardly worth going just to spend a few hours on the Argentine side. Simply a check mark on some bucket list. Or...Get a direct flight from Rio to BsAs.

it's kind of a long story, but my husband and i are not check off bucket list people. we are going to a business conference in buenos aires and added on rio. my father (it sounds quite silly to say but it's the truth) loves to travel on a time crunch and although we wanted to spend 1 extra night in Rio, he really insisted that we go to the falls. since it's his 60th birthday trip (timed nicely with the conference) we are indulging him. so that's why we'll have to be happy with what we're able to see because we really wouldn't have gone to the falls in such a time crunch, so it's better than nothing! ;)