Kudos to you for adopting a realistic approach and making preparations that will enable you to remain professionally engaged and productive despite an uncertain prognosis. I admire your resilience I am assuming that you are trying to think of alternative career paths that you could pursue if your mobility becomes an issue in the future - and you want to remain in the maternal/child realm of practice. Is this accurate?
One that basis, there is one option that you may not have considered - genetic counseling. This is a 'new' profession that came about as technology has advanced. It does require a Master's degree, but a BSN is one of the approved undergraduate degrees for entry into a graduate program. From what I have ben told, there are a limited number of qualified counselors available and the demand is growing. You can find more information here American Board of Genetic Counseling, Inc.
The requirement for certification will vary depending upon your teaching venue and state/local requirements. The problem with trying to make a career in sex education - it is a field dominated by the teaching profession, rather than health care. This is frequently an add-on responsibility for Health or PhysEd teachers, not a full time job. The basic qualification is usually a teaching credential for that area. You would have to do some 'cross-over' education to become certified which may include completion of a teaching practicum associated with a teacher preparation program.
If you want to stay in a 'nursing' field - your options will be determined by the amount of education &/or certifications you can obtain. If grad school is an option, then your options are greater. You could move into an administrative role - either clinical operations (nurse manager, director, etc.) or a support area (case management, quality, education, etc.).
Best wishes for your continued health.