There is a pattern for sale on Amazon with an image of the back of the pattern with the yardage requirements that includes King size. That may be helpful.
https://www.amazon.com/Double-Weddin.../dp/B011SFMI3C
I have hand pieced a double wedding block or two. Pin the curves and you won't have any problem at all on the machine. You will get used to the curves and then wonder why you were worried. After sewing up a bunch of curves, you will find sewing the straight edges to go more confidently into the future. And the double wedding ring quilts are beautiful! Sounds like a great project!