Yes you can delete the snapshots while the VM is running. It will take a while - maybe 1 hr due to the size of them. It also depends on the type of storage you are using etc....
If you are going to "delete all" make sure you have enough free space on your datastore as from my understanding and calculations - you will require an additional 50GB of space while the 4 deltas are committed to the base vmdk.
If you have the option of powering off the VM - power it off, delete all the snapshots and then power the VM back on - it will be quicker and reduce the risk.