We charged everything (and I do mean everything) to our room keys for 10 days -- including beers at Biergarten, beers in England, beers at the Barefoor Bar at the Poly Volcano Pool... smoothies, gelato, pretzels, Mickey Head Ice Creams, popcorn, and pins-- everywhere... Oh yes, we ate meals too! I am sure a few do not accept it, but we charged all the items we bought at DD also. We personally never found a place that wouldn't take it-- no matter how small.
Upon check-in, I told the CM I wanted to pay cash. They told me that the charges would be put on the CC at midnight the night before checkout, so just to reconcile with them before that. I went a few days early when I felt my total was close to $1500, took care of it and started again with the $1500 to charge. Luckily I didn't get there before checking out...
One strong suggestion-- be sure to check your KTTW when you get it back either at a TS (since they take it away.) or especially if the bartender holds it for a tab. DH was given the wrong guy's card after watching football and drinking beers for a couple of hours at Barefoot Bar. (It was charged to the right account.) We didn't realize it until we were done with dinner and the front desk fixed it immediately. No problem, but it is a good idea to just check the name.