By May or so, you should be ready to find a cofounder (Choose someone with some money, that you trust), and release a your own project, which is very similar (but not legally identical) to their idea.
After you get some initial traction, take off, and move to Silicon Valley, but leave your new co-founder behind. Maybe send him off to run the sales division in NY.
In SV, meet up with some charismatic bigshot (Preferably someone who had their own company before) to gain some publicity. Use him for intros to VCs. It's OK to party with him a bit.
When your Cofounder later comes to SV, dilute his shares to the point of basically kicking him out of the company.
Don't be surprised if the bigshot gets busted for drugs at a party at this point. He is Charismatic, after is.
At this point, you'll want to be careful- You're about to have some lawsuits.. Your Co-founder will sue you, as will the two college guys you're working for now.. But don't worry, your company is now on the road to success, and soon you'll be on the cover of TIME.
Yet, I probably will start working on a similar project like you suggested.(Although I have no intention of screwing over two harvard twins by stealing their idea)
They're not going to want to go with a whole new team unless you're very very behind, since they'd have to train them up.
But don't expect a payout from these guys. They're likely not to go anywhere, and you're playing "agressively" by taking so long.
So.. Do it if you enjoy it.
In this case, they are your bosses. I would just try to explain to them your situation. It might be time to quit or find another job.
Things I plan on doing today (Send it the same every day, as early as possible): (i) Homework - Required by school (ii) Reading 'X' chapters of a book, or Reading blog, code etc - Knowledge Acquisition To Help With The Project Or Personal Improvement (iii) Chores - Things that need to get done to live your life (iv) Thinking About The Project - This is how most "Features" get done. (v) Coding - Like 'Planning on adding approximately 100 lines of code'. To be clear, this is a fake measurement that is of no use to any developer, but for non-technical people, this is worth a lot.
And just before ending your day..
"FYI - I added 120 lines of code. This makes it 400 lines of code for this feature :)"
P.S: "e1ven" idea is much better :)
Just because they aren't technical doesn't mean they can't provide you with evidence of their input. Ask for more detailed specs, Spellchecked and proof read copy, mockups, copyright free images to use. Anything that will that will speed up the process for you and prove their commitment.
Ask to see evidence of their attempt at marketing, surveys with potential users giving feedback on proposed features, active twitter accounts networking, competitor analysis.
You need to get them to prove they're not useless. That they can contribute even outside of development.
If it turns out they ARE useless...you know what to do.
Have you given them any project timelines estimates, like "this feature will take about 30 programming hours to get roughly implemented, and I'm working 10 hours this week on it..."?
What they are, or are not, doing is probably not directly related to what their expectations are of you. Maybe they just have no idea how long it takes to get stuff done and you need to give them better guidance.
No, it wasn't expected that I would be working full time on this and yet they insist (with daily reminders) that I implement things faster.
Actually most estimates I've made tend to be off by around a few hours, but since I give them estimates in days, this isn't much of a problem.
Stay legal, of course. If you have signed agreements do not do anything to break them
tl;dw Steal their idea & make billions.
(just in case it's needed... no. not a serious suggestion)
edit: somehow missed e1ven's post. do that!