Your writing seems to be good enough. Just convert that into spoken words. Anyways, I don't think a Brazilian client would have higher expectations than a native English speaker, no offense to anyone. I am pretty much sure the Google could give you a lot of spoken business English practice for free. Just drop the words "spoken business English practice" on Google search and I'm pretty sure the world of spoken English would be at your fingertips. I put these words into Youtube and the first couple of videos seem to be really good. Have a look! Just be yourself and do what you can tomorrow!!

Just talk slowly and be friendly, Brazilians like it (Believe me I know, I'm one of them). If you have difficulty Spoken English don't use big words. Be simple and direct. If you want pulling chat, praise Brazilian cuisine. Say you love BBQ and have always wanted to eat feijoada. Good luck tomorrow =D

If you want my advice call him today and tell him u know Karate and if he will ask u tomorrow anything front your boss you will hit him strong :(