I really hope you find a way to go to your son's wedding. I know that it is expensive to go to Brazil, but on the other hand, August is low season there because it is winter. If you start looking now you might be able to find a really cheap deal. I just went over to Bootsnall.com (a travel site kind of like Lonely Planet) and since I didn't knwo where you live I just typed in DFW (Dallas) because that is near where I live. DFW to GRU (Sao Paolo) Leaving on a Wed. and returning on a Monday (mid-week flying is cheaper) I got $837 on American. THat is pretty cheap to go to Brazil; I know because I was trying to plan a trip there a couple years ago and couldn't get below $1000.00. If you dont' have a passport, apply for one NOW and you might have not have to pay for expedited service. There is a backlog due to new passport requirements.
Also try kayak.com for tickets; it is a comparison that will bring up several different sites at once. (Orbitz, Travelocity, etc.)