I agree with your whole trip experience and tips. The only thing I'd add, in particular for photographers, is silica gel. With the rainforest atmosphere it's inevitable that moisture will get in your camera. Even more so, when you're taking your camera from an air conditioned lodge to the heat. Thus, have some of the silica gels in your camera bag. This will certainly come in useful. Another thing, take your camera with you to breakfast, so it has some time out of the AC before you set off on your day. It will keep steaming up and you need the temperature to adjust. It would be very annoying when you have the perfect shot to be steamed up! Here are some pics I got in the rain and humidity in Andasibe.