You can use both for that one day, but you do need to check in before your QSDP credits are available. If you use a QS before your DxDDP credits are gone, just be sure they are deducting a QS credit and not one from your DxDDP plan. This might get messed up, so you may want to get a print out from your check-out hotel with what exactly is left on your plan. If they do make a mistake and you have no credits left for your Dx meal, just charge the DxDDP meal to your room and get guest services at the resort to fix it.