I've done a mixture of ship tours and private tours but in Africa where infrastructure, road conditions, plus it was a tender port I would have stuck with a ship tour. I guess you need to weigh up the risks. Some of those passengers need to be thanking the American couple as they were the only ones to have any sort of card with them to pay for stuff. Could have been a very uncomfortable time if noone had a credit card.
I was on the Ruby Princess in 2012 in Casablanca when there were several hundred passengers that missed the deadline for the ship departure. They were all Princess ship tours so hence we waited several hours for them.
Also Philip Island on Grand Princess last year again we waited for for the ship tours and they were late back too.