We recently went to Chogogo and had a good time. You should enjoy it. Take water shoes for the shore and a snorkel and mask. I didn't really think fins were necessary, even though we had them. I think the taxi was $10 each day and it was cash only.
Another thread on here:
I will say that we were one of the first one there that day (9AM-10PM) and my wife got worn out in the sun all day. So I'd say go later in the day. They may eventually turn people away, but there's not much escaping the heat, just fyi.