Ever since I first saw Star Wars, just from the way Ben and Chewbacca acted in the cantina, I had a feeling they knew each other. When I heard about Wookiee senators in Episode I, I thought, "Aha! Chewbacca met Obi-Wan on Coruscant as an Ambassador or something." Then someone reminded me that it was BoShek who introduced them in the cantina.
Still, Ben could have gone there knowing Chewie was likely there and simply asked Bo if he'd seen him around.
For some reason, I don't consider this huge spoiler material. We know the kids are delivered to safety, we know Chewie's in the film. A big spoiler to me would be the revelation about Anakin's father's identity. (Chewbacca, right Mr. Mayhew?)
One thing's for sure: If I see Chewie EXACTLY as he appeared in ANH, bandolier and all, I'll be thoroughly disappointed. I see no reason why Chewie can't have a costume change in thirty years.