Hello,
I moved your post from Workstation Pro to VMware ESXi 4 there's more likely vSphere users in this forum.
Can't exactly remember the feature set on vSphere client with ESXi 4, but there's a "Consolidate" option nowadays under the Snapshot menu that should do this.
Another way people resolved this in the past was by adding an extra snapshot and then choosing for "delete all"
Best not to mess with vmkfstools command line on live VMs unless you are familiar and comfortable with it and yes the command you are listing does require a power off (it's the wrong command for committing snapshots too, you're doing a clone)
--
Wil