Okay, so I currently work at a top 10 law firm as a paralegal, and I'm also considering a dual degree and I can hopefully give you some insight. First and foremost, I highly recommend NOT signing up for a JD unless you know what you are getting into and you know it's what you want. I've spent 3 years here because I took that long in weighing my options between law school and an MA. It's not a decision to make on a whim. I've seen so many of my friends end up miserable because they didn't think it through carefully. In that same vein, getting a dual degree is really inadvisable unless you have a very clear idea what you would use it for.
But on the subject of dual degrees - you say it's not an option for you because the schools offered by your program are weak programs. What about an ad hoc? For example, SAIS has official partnerships with Stanford and UVA, but they've also assured me that doing an ad hoc is possible, if the other school agrees, and a number of institutions in the top 14 have confirmed for me that they allow ad hocs (though I have no idea if this policy varies by school, etc).
Jumping back to law- the general consensus here that a JD locks you in to a certain kind of career does have a lot of truth to it. It's a profession, so that shouldn't be too, too surprising. I do think having a dual degree could help overcome that a bit, but if doing international human rights law is the only way you'd be happy as a lawyer, it's a risky proposition. Could you be happy working in big law? If you go to law school and have loans, you will have to work in big law, assuming you go to a prestigious enough program to get into a big law firm (genuinely not trying to be condescending- when I asked my firm's recruiter about her thoughts on the JD, her response was 'we have a list of 15 schools we recruit from and throw the rest in the trash unless you know someone'). I see a lot of associates work here for three years and then bail, because they're putting in their sweat equity to pay off the loans.
That's not to say that there aren't really interesting aspects of big law. I work in the International Arbitration group, and I love it. It's amazing. Even if it's not what I'd want to do forever, I could see myself being happy with it. And even if the big law hours here are grueling, I absolutely love the type of person that's drawn to this field, and really enjoy working with them. So a dual degree is something I'm considering closely. If big law is a job you think you will hate: run. Literally last November a dude in DC jumped off the roof of his law firm's building. If you do not like the people or the work, it will be hell. All this being said, you are just out of undergrad, and it seems like you're really over-planning things right now (why are you already stressing about supporting a family?). What you're interested in is pretty likely to change. I only graduated 3 years ago, and my interests have strayed from where they were originally.
(Also, on the subject of admission 'hooks': your admission to law school is 90% LSAT and undergrad GPA - LSAC does NOT factor in graduate GPA - and from what I've seen, soft factors aren't really useful unless they're tied in some way to the legal field).