Help with a itinerary for traveling with my 6 and 8 years old kids

In Verona: The Roman Arena, the Roman Theater, Castelvecchio, The Duomo, and The Basilica of San Zeno Maggiore. For accommodations try Hotel Torcolo. I'd spend at least two nights in Verona.

So 3 nights in Milano, 2 nights in Verona (parking difficult), 3 in the Dolomites, 3 or 4 in Salzburg, half a day in Innsbruck, 5 or more in Munich (parking extremely expensive) including a day to the new castles near Fuessen, (Italy is south of Austria), 5 in Switzerland, Lichtenstein is a non-event and you don't even get a stamp in your passport, and a minimum of 3 nights on Lake Como somewhere is a minimum of 24 nights.

You say you will have 14 days.

Is that 14 days sightseeing or is the first one flying from somewhere (where?) to Europe and landing on day 2, like most folk? And is day 14 sightseeing or is that the day you fly home on which you have to return the car, get to the airport and check in 3 hours before you fly, like most folk? So do you only have 12 days? 12 days is usually 13 nights....

It looks to me like you have twice as many places to go as you have time to do it in.

How much will the children slow you down?

I will be flying in to Milan on August 5th from Greece and flying out on August 19th from Milan back to Greece. So Italy Dolomites and Austria only?

Hello tasocian. You will have 13 whole days. If you will fly to Milan, and fly from Milan, and you will drive a car, I recommend : do not travel a very long distance from Milan. I suggest : do not go to Salzburg or Munich or Fussen. I suggest : travel in northern Italy, and Switzerland.

Nigel points out an important reality: too much to do and not enough time; kids will slow you down and parking/driving can be an expensive hassle. Other than that....

Aug 5 - arrive Milan and rent car; go immediately to Verona. Be aware you can easily do this by train; Stay two nights
Aug 7 - to Lago di Garda. Malescine seems to be popular. Going there the first time myself in June.... Hiking, ferries on the lake, etc. Stay three nights
Aug 10 - to Dolomites. Do you have a plan where? We like the Val Gardena a lot and so did the children of 2 and 6 we accompanied there with their parents last summer. You can ride lifts and gondolas and even a funicular to fabulous hiking and vistas. Stay at least 4 nights in case bad weather thwarts your views.
Aug 14 - to Switzerland or Austria. Austria is closer and probably less expensive. You have 4 nights. Then comes the hard part: a long-ish day traveling back to Milan, 5 hours in train; 4.5 by car. Edit: this drive time is from Innsbruck.
Aug 18 - Milan
Aug 19 - fly

I suggest you go to Rome2Rio.com and plug in itinerary options and see what travel times are. You could sub Lake Como for Lake Garda and change your order of travel, then go to Switzerland, for example.

Factors to consider: Travel time whether by train and bus or car; Taking a car into another country; Exchange rate; What your family likes to do; Tolerance for long hauls in the car; Staying long enough in a mountainous location that one day of rain won't spoil the time allotted there.