Welcome to Argentina!
I have chartered a sailboat in Angra, and it was great!.
We went only one week, so we could only go to Isla Grande and the islands near by. To go to Para Ti we would have need another week.
It is a great place, I recomend you to go.
We went in march, last year, and we would have need 2 or 3 degrees more of heat, jajaja.
You should be checking the weather and choose the departure time according to that.
It rains a lot up there.
To start checking some boats, here goes some pages.
we rented the boat to Ricardo, the owner of this vessels.
He is a great person, all worked out perfect, and he arranges a taxi to pick you up at the airport in Rio, then takes you to the supermarket, and then to Ricardo´s house where he has the boats.
They are not fancy boats like beneteaus, but they are cheaper.
yacht charter that Copacabana recomended you
and you should check more that comes googling on line