I have been learning Chinese (not Chinese beginners? im in year 10) for several years (years 5-10), and honestly, I think you should do go for it. You have already established the foundations of language learning, and because you are learning Japanese, many of the characters will be the same. I'm quitting Chinese after this year (i'm in year 10) because of the workload of the other subjects I have selected, and also because I don't want to do such repetitive work (i.e memorising vocabulary items). I enjoy the language and I especially enjoy the fun of it (once you become good at it), but I just don't feel like its a subject I enjoy LEARNING. In Chinese you have to learn tones, which can be particularly painful, but also their vast array of grammatical features. I feel like Chinese is a very rewarding subject, much more so that Spanish, as there is a larger proportion of Chinese immigrants in NSW as opposed to Spanish immigrants. At my school there are a fair few of international Chinese students, which I (used to) occasionally practice with. ANnnnyway, that is just my experience learning Chinese, you may or may not be able to relate, but I hope it provides some insight and direction towards your decision.
