That is true that no mention of a ship is made except that Gerard had served with Quentin on board a ship, but the name of the ship is not mentioned that I recall.
However in the case of the Children, that plotline is made to be very important in 1970. You are led to believe that not only was David and Haley in danger in 1970 but that it was somehow a rehashing of what happened to Tad and Carrie in 1840. However in the end, the children are really not prime players in this segment. Carrie is more so than Tad, but neither are put in the kind of danger that Daphne seems to fear for David and Haley in 1970, yet she clearly asks Gerard if it has to happen like it did before? In the end, you wonder why the children were involved in the whole matter at all in 1970. Unlike with 1897 where the events of 1968 and 1969 play a role in the plot line of the past, with the concern being for David in the future, no such thing happens with this plot.
I'm wondering if it's possible that they simply just deviated from the original plot for 1840 they had earlier sketched out. The 1897 story changed almost instantly from what they originally intended. It was suppose to last only three months and there were apparently many differences from the 1897 "bible" and what eventually transpired on the small screen such as, I believe, Jenny being Edward's wife, not Quentin's. But almost immediately, they began to shuffle characters around when something else popped up (like Diana Millay becoming available, so they rehashed the Laura story). And, of course, as viewership skyrocketted, they just continued to add more and more until the 1897 tale went from three months to almost nine.
So maybe that happened with the 1840 plot. It was laid out on paper, but the red pen quickly altered it without any thought to consistency and things already made clear in 1970 (such as Tad and Carrie dying at almost the exact time Quentin I did back in 1840; what was the importance of the Java Queen in all this; etc.).
Gerard