It's kind of hard to give suggestions on what an entire chapter should be about. Try just thinking about what needs to happen to get from A to B. Where is your character going next and what is he going to do there? What are his motivations for doing so? How you handle the wanted poster situation sounds like it will have a sizable impact on the story, and I feel like it will affect what the next chapter is going to be about. If you already know what you want to happen sometime in the future, think about the best way to get there from where you are now. How the Pokemon center staff react also seems like it will impact the story some way, and will inevitably depend on what your character does next. Will he deny any wrongdoing? Will he run away? Will he turn himself in? (Hell, did he even do it?) In this case, it's most important to think about exactly what your character would do. If you don't know the answer to that question, or any of the other ones above, then I suggest you go back to the drawing board and work on your plot outline before you worry about writing the next chapter.
Same deal for whether or not to bring his parents in. If they're important and have an impact on the story now, then do it. If they won't matter until later, then wait.