I had this very same issue at 36 weeks. I did opt for the csection, in the hospital and I had it done that day. Keagan had 4.2cms of fluid and was breech. He could not move because of the lack of fluid. He also had a knot in his cord and the placenta had started to deteriorate and that was the cause for the low fluid. If I had waited, he might not have made it another week.
Best of luck and I hope you get the birth you wanted but more importantly, I wish you a healthy and happy baby!