I do have the book to hand, and it is "
elven", so the mariners are definitely Elves. Sorry to burst the interesting bubble about a specific number.
From the context, we can assume that both their goal at home and that of their journey to the Dark Marches, where they fought, are located in Faery, since Smith was in Faery when he saw them there. So the connection between the Elves and our world is not through their journey. It is Smith himself who makes the transition from real life to Faery, by way of the star, and he made the journey by foot or by horse.
On closer scrutiny, we therefore have no additional Straight Path, no doorway from one world to the other, no time transition - though it would have been interesting to explore those ideas more...