Merlin's right (of course) ... simplicity is key.

I set people up with GTD for a living, and the number one mistake I see new GTDers make is to to choose 10+ different contexts and try to sort all of their tasks into them. I'm sure someone, somewhere, genuinely requires 10 contexts, but "In Microsoft Word," "In Firefox," "In the Kitchen," etc. contexts easily get out of hand.

I have two main contexts, "Calls" and "Errands." (I also live in another state part-time, so occasionally an "Utah" context is necessary.) That's it.

When managing other people, your Waiting On list becomes key. I'd suggest putting a binder out somewhere easily-accessible with a sheet for each person you're in charge of (alphabetized) so each person can look for themselves at any given moment what you're still waiting on them for. Make it clear from the start that they are responsible for anything listed in that binder.

Mainly, no matter HOW busy you are -- and you will be very busy -- you need to schedule a Weekly Review with yourself. When you first start out, it might be an Every Three Days Review. You've got to take everything that you've captured and make it actionable, and you've got to follow up on things you're waiting on.

Put all of your due dates into a private Google Calendar and setup SMS alerts to your phone. Every Sunday, look at the calendar and make an action card for each upcoming day of the week. (4x6 index cards work great.) If there's anything time-sensitive during one of those days, jot it down. This creates a multiple-reminder system that makes it difficult for things to fall through the cracks, but is still simple to use.

Give your short timeframe, you might want to hire a coach to get you setup. Developing a solid, trustworthy organizational system that really works for you is a process, and starting out with someone experienced on what works and what doesn't can shave months off the learning curve. (Shameless self-promotion: I'm available! marina at sufficientthrust dot com.)