Traditionally white chocolate is made with cacao butter, but if you don't have any, you can use coconut oil in it's place. The white chocolate flavor comes from the cacao butter, but again, if you want to play around with using coconut oil, go for it! Just know they will need to be stored and will melt more easily than if using cacao butter.
If you don't want to use macadamia nuts, which are my personal favorite, you can use cashews or coconut butter instead. If using a macadamia butter, cashew butter or coconut butter, only use 1/4 cup, in place of the 1/2 cup of chopped nuts.