So I thought I should wrap up the thread.
Just to be clear, NO we did not do the check-out dive. However the requirement lead us to believe that the other people we would be diving with would be half decent diving. To make a broad generalization, the quality of divers we have been diving with in the Philippines to that point (and mostly after that also) was actually very very high. I'd never before dived with so many random divers with good trim and proper kicks.
No we shouldn't have gone in the wreck once we saw the other divers underwater. I justified it to myself at the time that although I expected the 40m long prop shaft to be a world of silt, that it would all be OK after that. I also felt (as arrogant as this sounds now) that the three most competent divers on this dive were the guide, and my wife and I. I thought it best to book-end the group to avoid a real cluster. I stayed close enough to the wife to physically grab her at any time if required, which was part of my risk management plan made up on the spot. And despite the fact that we had reels, we didn't use them. Why? I guess because the dive was somewhat of a "swim through" by plan (although I hate that term) where we would start at the deepest point, make our way through the ship, and exit at around 20m or so. If it went to hell in a handbasket during the prop-shaft, then it's not that hard to follow a straight tube backwards. After that point we had been promised lots of exits. Running a line would have meant leaving it in place. Not that I care about the line, but if every diver every day did that, the wreck would be a spiders web within days.
TSandM is right about it being a dive from which someone might have not returned. I agree with that completely. Since the original post my wife and I have spoken about this dive a lot, and we have agreed that neither of us was worried that we ourselves could not have gotten out, despite the silt. At worst case would push ourselves to the front of the pack to some clear water. We were slightly concerned for each other, but we were really really crapping ourselves about the other divers. I can't imagine someone who has to crawl or walk through a wreck would be very comfortable in zero vis. I think I was most worried about some dealing with some novice panicked diver .
What was almost more disturbing though was that we had a sit-down with the dive-shop owner the next day after we made a small comment to the resort we were staying at. Long story short, he didn't seem to give a damn. The biggest concession he made was that maybe they need to take a little more care in which divers they allow in. I only wish I had a go-pro video of the dive to show him, but I abandoned that 10seconds in when I realised I couldn't afford to split my concentration. I've since spoken to other very experienced local divers who also love that dive, but say they only ever do it with divers they know and trust. The fact that a shop took in divers who didn't have basic buoyancy control makes me shake my head.
The fact that I trusted them not only to vet divers, but also to provide accurate instructions all on the first dive I'd ever done with them? Lesson learnt. I feel very stupid now. They say familiarity breeds contempt. In this case, I transferred professionalism and trust from one dive op to another based on a recommendation. Stupid.
I failed to thumb a dive that was obviously a cluster-F due to a desire to do a certain wreck. Stupid.
I dived with dangerous divers in a dangerous environment. Stupid.
I ignored my training because I felt comfortable. Stupid.