I thought those characters where introduced in Eclipse, but if I am wrong, it doesn't bother me that they never made an appearance in New Moon. There were so many new Characters introduced in the latest movie, i think meer ( and two important) characters would have been too much for just one film.
Well, I wasn't that upset because they, the Clearwaters, weren't really part of the movie. Well, actually, Harry, Sue, Leah, and Seth were all mentioned in New Moon. Though, they weren't really a major, maybe not even a minor role. They were really just mentioned because Bella stared spending a lot of time in La Push, so she got to know/meet most of the people in the "werewolf clique", of tribe. Harry was really the only one who they showed in the movie because his hart-, hart attack lead to a lot of other things. One of these is Leah and Seth becoming werewolves in Eclipse, and if all of u already read Breaking Dawn, Charlie and Sue eventually got closer, with Bella saying, "the werewolf's mom with the vampire's dad". So, yeah, hope this was helpful. :D