I followed this link and submitted the forms for both of us since we both have CPAP machines. The response back from HAL was the same for both of us was:
"Our guests often bring sleep apnea machines on board. Holland America Line staterooms have standard US outlets. However, as the outlets are usually on the dressing tables and not near the head of the bed, we do recommend bringing an extension cord."
Bottom line, we need to bring our own extension cord.