What Next from Kuaile Hanyu Book 3

Hi, My kids are about to finish book 3 of kuaile hanyu which primarily geared for young kids, and I am thinking to having them go to HSK next. I am thinking about HSK 4 or 5, and leaning toward 5. From my understanding HSK5 is where it starts to matter as qualification by instutions. They are middle schoolers now and I actually have studied Chinese alongside them out of my own passions, so this is for me as well. Would that be too big a jump for them? Is HSK 5 suitable for kids around this age? Any suggestion welcome.