It depends on whether the virtual disks are thin or thick provisioned. With thin provisioned virtual disks you will most likely not be able to delete the snapshots, because the base disks may grow. However, with thick provisioned virtual disks, the base disks will not grow any further, so deleting the snapshots should work without issues with the VM powered off! Deleting the snapshot with a powered on VM will create helper snapshots, which will grow depending on the VM's activity, and cause an out-of-disk space issue.
André