Snapshots swell the size of my VM and periodically, when it is all running well, I like to pare down the size. I seem to recall a few versions ago that you used to be have the option to delete a Snapshot and all its "children" at once. Has that option disappeared?
Use the Delete All option to delete all snapshots from the Snapshot Manager. Delete all consolidates and writes the changes that occur between snapshots and the previous delta disk states to the base parent disk and merges them with the base virtual machine disk. Deleting a snapshot leaves the current state of the virtual machine or any other snapshot untouched.