Venice has two main ways in, one being the causeway from Maestri and the other the various boats. The causeway terminates in a large railway station and a mahoosive car park; no knowledge of bike security there. If coming from the other side, Jesolo or Cavallino, the ferry terminal is at Punta Sabbioni where there are bike stands. That ferry deposits you at Piazza San Marco.
Tourist hints: riding out of Munich Airport is a nightmare. Take the S-Bahn one stop (bikes allowed) to the South and pick up the Isar Radweg.
If visiting Venice, get to San Marco early and take the lift (about two Euros) to the top of the Campanile. You avoid the grockle rush, and the views are stunning.
Camp sites are spread along the spit from Sabbioni to Jesolo.