Hi tomairdrie,
There are 14 people booked on this trip - so it is big enough to have been cleared.
Casual lightweight clothes are the order of the day for warmer climates. We also recommend that you take a warm jacket, bathing costumes and good walking shoes. In addition, the weather can be cooler in Chile, Argentina and Brazil, so a cardigan or lightweight jacket may be needed. It can be moderately wet with changeable weather - so take a waterproof with you just in case.
Kindest regards,
Monty