We do split stuff all the time. When you check in, (have it figured out in advance) tell the person at the desk to charge xx.xx to one credit card, then charge the remainder to the next card. Then whichever of you is more comfortable, leave a CC for room key priveledges. Each of you charge your personal charges to the room key. Then every couple of days, go by the front desk and get a printout of your room charges. They don't add them up, but each card has a unique number and you can add up who charged what. Then go by the front desk again and each pay whatever you owe with your personal CC.
Also, like another poster stated, most of the time I have split charges is when friends visit me for part of my two week Ft. Wilderness trip. I just put the room bill and room charges all on my card and right before they leave, we figure out what their share is and we go up to the front desk and they pay that amount on their credit card. Then I put my card back on the account as the guarantee and finish out my trip.
If you are staying at a Value Resort, you need to do this every couple of days because that $500 limit adds up fast, but if you are staying at a Moderate ($1000 limit), or Deluxe ($1500 limit), every four days or the night before you check out is sufficient.