Try not to pick a framework technology first - find good people and they will develop in the framework that suits them best, according to a high level spec doc. It really doesn't matter what the prototype is built with as long as it's easy to pivot. You shouldn't worry too much about scaling for an MVP. Languages don't scale - platforms scale. As you get to scaling problems you can attack weak points as you go, maybe split the app into an API and optimize portions as necessary.
Of the frameworks you mentioned, Django is probably not the best choice for an interactive app with a bunch of external API calls as the core.
Java+Playframework, Ruby+Rails, Node+Express, are all appropriate and will come with their own unique drawbacks and advantages. Focus on the devs who will build it.