My advice would be to DIY rather than taking a tour. It's much nicer to walk the falls at your own pace. Since you'll be on the Brazil ide, if you have time, I'd recommend the Bird Park that's just outside the entrance to the park.

Also, it's expensive, but staying in the hotel within the park gives you early and late day access to the walk to the falls. It would be a way to maximize what you can do from the Brazil side and minimize the hassles. The hotel has a tour desk if you feel the need to have them book the boat ticket for you or the concierge can help.