The average audience member won't even know Mara Jade, Jacen Solo, or Anakin Solo even exist, so there's no point in mentioning them. At most, people might wonder who Luke's wife was and who gave birth to Ben, but that could all be explained away in a line about Luke being widower. Heck, you could just have a scene where Ben mentions his dead mother, just as Luke and Leia did in RotJ. In either case, Mara Jade probably won't even be referred to by name, but simply as Ben's deceased mother. Chewbaca is a trickier situation, because audiences know him from previous films. You could either bite the bullet and have a scene or two explaining the fact that he's dead, or simply have him appear in the new movies and explain away his survival via the EU. I hope they keep him dead, simply because the character was starting to become pointless by RotJ (so was Han, for that matter). Yes, he's beloved by fans, but I think most average audience members would be forgiving, simply because this is forty years later, and it makes sense that some of these characters would have died offscreen.