I will preclude this with the fact that I am not very wise when it comes to this, because I have yet to begin my first year of a masters degree, but I can give my (probably misinformed) opinion.
In terms of low-risk route in making your way up the international relatiosn ladder, that certificate you posted might be a good opportunity. It won't really get you an advancement in the workplace, but it will put your foot in the door and most importantly let you determine if you want to pursue a masters in IR or not. This would also be ideal if you discover that your other two fields of interest are what you actually want to focus on, but with an IR affilliation.
I think another thing you may want to look at as well, if maybe you want to get a masters in a shorter amount of time, is completing it in the UK, where a lot of IR programs are only a year long, and (somewhat) cheaper than large, private IR programs.
I think both computer science and finance would be useful masters to have as well for counter-terror (can't speak much to the finance aspect, but there are some great international finance programs out there, some which I believe you could do dual degrees with IR programs).
I, myself, have recently become interested in computer science mainly as a way to increase my job prospects and pad my resume. I believe this is something that you don't necessarily need a masters for in order to work with in the future. There are tons of free places to learn programming out there (MIT open courseware, codeacademy etc.) and what I plan on doing is creating an app or a website or something, gaining a ton of knowledge, and then using the actual product to showcase on my resume rather than a degree, while maintaining my IR master aspirations.
I think any of your goals are great for advanced education, it really just depends mostly on what you could see yourself studying in an academic environment the most. Just because you don't get a degree in one doesn't mean you can't further pursue goals at another later on.
Talon1025,
After reading about your background and and looking at your comments, this is my advice for you. Take it for what it is worth:
1) I completely understand that you are worried about the value of an international affairs graduate degree on the job market. If you would like to go into diplomacy/counter-terrorism, you should look at programs in D.C. These programs are near the agencies/companies where you want to work and you would have plenty of internship opportunities.
2) I am pretty sure that a Master's degree in Finance will not help you land a job in either diplomacy or counter-terrorism. Those companies need accountants but it seems like an odd fit.
3) Unless you are a true computer whiz or a hacker (like Mr. Snowden), I am not certain that a Master's degree in Computer Science will help you that much either. But this degree is probably much more helpful on the job market than an IA degree.
