HP RAID5 expansion effect on ESXi 5.1 host datastore expansion options...

I have an HP ESXi 5.1 host with 4 VM’s on it, I need to add another VM but don’t quite have enough Datastore space to feel good about it so I have a drive to add to the server to expand the RAID5 array.

I have to use the HP Array Configuration Utility via a bootable USB to be able to expand the array on the built-in HP E200i controller since it won’t work via the boot management interface to add this drive and am not sure how it will ‘Datastore’ reflect…?
Will the existing Datastore dynamically expand or would I have to add the extra drive space as an Extent?

I do not yet have foolproof backups of these VM’s (they’re all utility servers and am in the flow of this deploy…).
Along with the actual VM’s, I do have the ESX OS system logs stored on the Datastore (under a folder called SystemLogs) though and there’s the .locker folder also.

The host ESX OS is installed on internal USB flash so if I didn’t want to go the Extent route and simply wanted to wipe and recreate the Datastore with the expanded space…With all of the VM’s shutdown…
Can I simply browse the datastore and do a native VM folder (all of the files contained) ‘Download’ to a storage location on the server my VMware client is logged in from (which renames the ‘vm’.vmdk to ‘vm’-flat.vmdk) as a simple recoverable backup method!?
I’ve read that the .locker folder that contains the scratch file will just recreate but what do I need to do with the SystemLogs folder? Copy it before shutting down the host or just recreate it when I recreate the datastore so that the ESX OS config will send the logs to it fresh?

I’m actively working on this (download backing up VM’s now in prep for adding the drive) so timely answers would be really appreciated!