My first few times down there I carried probably about a thousand dollars

. Then I realized I never spent even a third of that, I just wanted to be prepared. Now I carry very little. In fact when I was there in December, I had decided to carry as little cash as possible. I had a $20.00 bill that I had left over from my Sept '07 trip in the little divider thingy I carry my ID and credit cards in, I prestuffed tip envelopes for bell services, the DME driver, and mousekeeping, but other than that I carried no cash. I had my room and the
DDP paid for, before I arrived. Other than using my credit card at the
Disney store in DTD to get my mom a new 2008 t shirt and me a couple pieces of jewelry in Mexico, I spent no more money down there. I didn't realize until I was getting ready for my May trip a few weeks ago that I still had that $20.00 bill from my Sept trip. Guess what, I got back from my May trip May 10th and still have that $20.00 bill in my divider thingy. Again I had my room and the DxDDP paid off before I went. I prestuffed tip envelopes (this time figuring what I would eat at each restaurant and figuring the tips beforehand). I over figured my tips and brought some home with me, even though I tipped 25-30% at a few places. I guess that $20.00 bill will be going back to WDW with me for a fourth time in Sept. Maybe, I'll find a place to spend it. However, I am again on the DxDDP and both it and my room are paid for. We'll again be carrying individual prestuffed tip envelopes for bell services, DME driver, mousekeeping, and the restaurants. We've been enough times that we seldom find any new souvineers to buy. I always carry two credit cards, but seldom use them anymore. Believe me, my house is full of Disney stuff and if I saw something I wanted I wouldn't hesitate to buy it, but would use my credit card to do so, then just pay it off after I got home. As long as I have my tip envelopes, cash is usually not necessary at WDW. Everyplace take credit cards.
When you check in, they will ask you if you want to put a credit card on file. If you do, then all you would need to carry to the parks would be your KTTW room key. You can charge anything you want on it and have it billed back to your room. Then you can either pay it off the night before you check out or just let the resort bill your credit card. The night before, they will leave an itemized list of your charges on your room door. If it's OK, you don't even have to go downstairs to checkout the next day. Just leave. Oh, yes, make sure you have enough money at home to then pay off your credit card.
I wouldn't take much cash and no travel checks down there. I'd either keep the cash at home, use credit cards down there to buy everything, then pay the credit card off when you get back or else maybe buy some Disney gift cards at the Disney Store to use down there.