a couple extras to add to the cost of the car rental ...
does that price you quote include the drop charge to leave the car in Austria?
Since you are contemplating a 3 to 4 hour drive right after landing, are you coming from a nearby country or will this be after an all night flight from the US/Canada/Australia?
If it is transatlantic is there one of the three of you who sleeps well on those flights and is immune to jet lag? If not you are well advised to reconsider a 3 or 4 hour drive while in zombie mode.
Each driver is required to have an International Driving Permit in addition to their valid home driving license. Each country has a method of acquiring them. In the US and Canada they are available for around $20 at AAA/CAA.
To drive in Switzerland where you would drive you need a Swiss Vignette which sticks to the inside of the windscreen, costs CHF 40, around 40€. To drive on highways in Austria you need an Austrian Vignette which sticks to the inside of the windscreen and costs about 10€. Roads in both Switzerland and Austria are patrolled for these vignettes, both by police and automatic cameras. Tickets are very expensive.
There is lots written about the perils of the dreaded ZTLs, zones in most Italian cities and towns where you must not drive, and where contravention will be caught by the cameras at every entrance, and for which fines are very high, to say nothing of the charges the rental company puts on your credit card for identifying you to the police.
Does your quote include the mandatory and voluntary insurances and waivers for the car, and any extra driver fees? Many credit card insurances are not valid in Italy.
If you are driving on highways in Italy expect tolls. There are some autostrada highways near Malpensa airport where there are no toll booths and you have to pay on line. That's your responsibility and fines are high, the entry and exit is monitored by cameras.
In order to drive in many cities in Germany your car needs to have a green Umweltplakette stuck to the inside of the windscreen. These are not very easy to get for rental cars so don't count on going into the restricted areas - they are patrolled by cameras and fines are high.
They say forewarned is forearmed. When you know the rules, driving in much of Europe is quite easy.
I do it every year. But you need to know the rules and expect the extra fees to pile up.
The train from Malpensa airport via Milan and Genoa is easy to the Cinque Terre but I've run out of time.
Happy travels