I would go with the 14s still. You could do the 18s but 8-18 means your DIN would be at the bottom of the scale and it isn't really worth it. Plus from my experience the royal family has really fucked up springs and my normal DIN is around 9-10 but my Jesters are set up around 11 to release right. I am around your height/weight and for a park ski I would definitely go with 14s.
Having a DIN setting that smack in the middle of the scale on your binding is what works best. You run into issues with releasing if your dins are close to the ends of the scale, top or bottom. Unless you want to tear your ACL's, get the 14's.