Not sure if you're still considering this, but I thought I would chime in. I've also been in your shoes before. It sounds like you have a pretty good idea of what you'd be getting yourself into with medical school, and I think its very mature to assess whether its the lifestyle for you. But I also understand your point about not wanting to be working on becoming an NP for longer than med school will take. Both pathways are a big investment of time and money, so its important to chose wisely. I would suggest you consider some accelerated MSN programs where you do graduate eligible to be an ANP. Many of these programs will make you put down a specialty when you apply, but I think most are also willing to work with you if you change your mind throughout. If you think you're interested in pediatrics or family practice, you could pick one of those after doing some shadowing, while knowing you can change if needed. One nice thing about APNs is that you can add something on with a post masters certificate - so you could become an FNP, for example, and then later decide to go back for another year or so part time to do the PNP.
Hows your decision coming along? You are welcome to PM me if you'd like some more specific info about this.