My wife and I just got back from a 2 week trip to the Galapagos Islands with one of those on the Galapagos Sky live aboard. Yes, the water was warmer than we expected ~77-80F except for a couple colder dives off of Fernandina Island. We had 7mm wetsuits with 5mm hoods and gloves. We could have used your 3mm wetsuits and been comfortable for all but the Fernandina dives. We only used the hood on 1 dive for the week. So that is the weather update. The good news is that we had great dives on an amazing live aboard. The only thing we didn't see was a Mola Mola, but there was 1 distant sighting by our dive master. We just weren't in the right spot at the right time for a brief glimpse. As for all the rest, we had good visibility on most dives. As too be expected, we had a couple low visibility dives and a couple high current dives, but for the most part the diving was great. It is definitely a challenge at Wolf and Darwin, and good gloves are a must. You will be hanging onto rocks in the current watching the sea life swim by. There was never a feeling of missing out because of El Nino, and multiple opportunities to swim with whale sharks, hammer head sharks, sea lions, and marine iguanas. Below is a link to pics from our trip.
https://www.flickr.com/photos/orcutt_pix/sets/with/72157655730736310