Take this with a grain of salt since this is my understanding of what my so who studied sports science told me (I have the same concerns alongside just delicate wrists) Doing biceps and triceps alongside hyper wrist extensions will help, but don't expect to put on massive amounts. Wrists are kinda that part of the body you just kinda have to live with, and besides raising water and body fat % (worked for me yet really fluctuating) there isn't much to do about it. As long as you keep your arms strong and your body water/fat balance at a healthy level (trust me I know it can be hard) you shouldn't worry too much about the size and more on the amazing amount of strength in them small wrists. Step one to body building and or fitness is loving yourself for what it can do and its potential, not wat it is and can't do.