How particular are you about your coffee? Do you only drink certain brands?
I haven't been there since some of the resorts changed over to Joffreys, however, the posts I have read regarding coffee say it is a great improvement over the previous brand. The resorts also have the usual little packets with sugar and creamers available.
We usually drive down from NY, (we usually drive everywhere!), so I always bring a can of my brew with me, and pick up a container of milk somewhere along the way. I'm not overly picky with my coffee, but I don't want to be surprised by something I don't like...so I just bring my own. I do need milk - not half & half, not creamers, no extra flavorings - just coffee and milk.
So you may like what the resort offers, or you may not. I think Folgers(?) offers coffee in tea-bag type packaging - if you like their coffee you could throw a couple of bags in your luggage.
I've also read that Starbucks has taken over the Main Street Bakery in Magic Kingdom and that they are also located in Epcot somewhere. So...if you are a Starbucks fan (I am not), you may be able to handle the resort coffee for the caffeine and enjoy a cup once you get to either of those two parks.