Kelly
I don't think you answered this in your other thread. How long do you hope to take on your journey south - and north - and how long do you want in Venice?
Are you planning on parking in Fusina and sleeping in your caravan? Or would you park and leave and spend the time in Venice? As you have never been there (my favourite city in the world so far) how long do you project the Venice stop to be? Will you leave the caravan and explore other parts of the Veneto?
Are both of you drivers on the trip? EU licences?
The size, height and weight of your rig will affect your motorway costs. What class is your rig in Denmark? Height?
As you travel, do you want to cover the distance quickly, so using Autobahns and Autostrada a lot, or do you want to take your time using mainly "B" roads which will be more scenic but considerably slower, with roundabouts, 50kph town and village speed limits (sometimes as low as 30 or kph, single carriageways and everything that a rural route involves?
I'm sorry for so many questions but they are all important. If we can pin you down a bit we can offer much better answers.