Hi,
If you want to leave your VM powered up during the copy am afraid thats not possible but if not you should have plenty of options.
Could use a GUI tool like winscp / or veeam's fastscp. Winscp is probably easier - quick download and basically all you need
to do is create a connection to your esx host on it and it will present an explorer-style window where you can drop and drop your vm's across to your NAS device
