Wow, you've got a lot on your plate that you'd like to do.
In order for you to be useful overseas, you'll need at least a year's experience because you'll need to be comfortable in your own field. There are various routes to doing this and the fastest would be what's called an entry-to-practice program where you receive your RN license and your Masters degree to become a Nurse Practitioner/Midwife. The shortest time to do this is about 2.5 years. You can do a Women's Health NP or become a Certified Nurse Midwife. If you want to become a Neonatal Nurse Practitioner (sick infants), you would need at least an additional year of school plus you would need two years of RN experience prior to starting (or before your clinicals) working in a Level III NICU in order to become board certified with the NCC (indeed, I would wager that all programs require this experience; I've done a thorough search on all the NNP programs a few years ago).
So...if you were to get into school this fall, it would be 3.5 years of school, 2 years of RN experience in the NICU, 1 year doing midwifery, 1 year of doing NICU. 7.5 years total at the barest minimum, which makes you age 32...this is not to only mention the fact that you may not be able to get a job into the NICU right away as it's a difficult market for nurses right now.
I think it would more worthwhile for you to choose one specialty and add another specialty in years later if you still want to pursue it. It's a lot of money and effort for two separate specialties because you probably won't be able to keep up your skills in both since it'll be very difficult, if not nearly impossible to work in both at the same time.
If you want to work overseas, becoming a midwife or women's health NP is much more useful and marketable because there is a great need working with low-risk women in pregnancy (high-risk pregnancy has a high mortality rate due to lack of resources). NNPs work with sick infants and generally low-income countries don't have the resources to take care of them. It doesn't matter if you have all the knowledge about them: if you don't have the equipment, you can't help them. It's about $5000 a day to stay in my NICU and there's no way that low-income countries could afford that kind of care to one patient.
You would be more effective gaining skills before working overseas, but I wouldn't dissuade someone from going out for the Peace Corps. My sister is doing it now in Morocco (youth development) and she loves it.
If you want to go to the big name schools and hope to get your loans paid off, realize that you'll have to work several years in low-income areas in the US. Again, NNPs wouldn't be able to do this (I've looked): only primary care specialties like women's health, midwifery, or family nurse practitioner.
Are you married? Is your spouse on board with your dreams? If you're not, it's hard to predict when you find your special person as anyone in the world will tell you. I liked to plan a lot too (to the extreme like you : ) but I can tell you that life takes you in many turns you never expected (totally cliche I know). If you want to do everything you listed, you probably wouldn't be able to have the children as young as you'd like.
As for what you should do? I would shadow a few NPs in various specialties around for a day and see if you like it. I was fortunate because I knew exactly what I wanted to do from the time I was a senior nursing student. I applied for jobs at the top NICUs 6 months before I graduated, have been working for a few years, and now am going to UPenn for my NNP. I have absolutely no regrets (moved across the country for the job and two years later am married to my DH) and I feel extraordinarily lucky knowing what I wanted to do and having so many mentors along the way.
Here is the google docs spreadsheet I did a few years back comparing all the schools that did NNP (it's a bit outdated). You can compare cost, etc, although it assumes you would already have your RN license.
Best of luck: keep us updated on what you decide. There are plenty of resources around AN for you. I would also check out the "students" tab and click on the graduate school forum. Most of the students there are in your place.