Vienna is the only outlying city in this itinerary, it's a long train ride from Ljub or Bled. Are you taking train or driving?
Be aware that the train route doesn't connect you from Slovenia to Italy. You must go up to Austria, then west, and down through Verona. Time consuming.
Vienna to Bled (via train), change trains in Villach, Austria (5/6-hour ride?)
Bled to Ljubljana (via train)
Ljubljana to Venice, (via bus) bus seems to be the fastest and most frequent method to get to Venice, while train sounds scenic but infrequent and indirect.
From Bled to Venice, you can take the scenic Bohinj Railway to Nova Gorica (use Bled Jezero station, not the mainline Lesce-Bled), cross into Gorizia by local bus and then take a train to Venice.
OK, this has got me interested, how much travel time would this be?
EDIT- OK, as nice and pleasant as the Bohinj Railway looks, it doesn't run regularly (1-3 times a month) and we're not going to be around when it does run. If they could secure additional funding or, get the gov to subsidize, that route would be a hot tourist attraction for international travelers and could be quite lucrative.