The title says FNP + CNM, but the questions asks FNP + WHNP, so I'm a bit confused as to what you are asking. I have a colleague who was a Midwife, got her BSN, went to FNU to get her MSN/FNP, then went to FNU and got her CNM as a post-masters certificate. I know of several others who have both the FNP and CNM, but I don't know the details of how they got both degrees.
I don't personally know of folks who have both FNP and WHNP, not sure why you would need/want WHNP if you are already a FNP, but that's because I have not researched the different scope of practice for the two.
I started out OB-GYN (WHNP now) years ago and realized that I had to continue on to get my FNP in order to have a career that worked for me in my area.
I did the right thing and it worked for me. I see many who either start out CNM then go for their FNP. You need to research to see what is available in your area and if you plan on not moving. IMO, FNP is what worked for me and have found this is true for others as well. A dual-certification is something some NPs are doing and they seem to be able to find lucrative jobs.
Research and see what is the most important career path you wish to take. Talk to others in "real life" and see what works for them.
Good luck as you consider your career pathe.