Right now we are planning: Munich- Vienna- Tura Luka- Bratislava- Salzburg or Munich
My gut feeling is that (depending on what languages you speak) it might be better to do some of the smaller locations while you have a European driver who speaks German traveling with you.
I think you could get by in Vienna without speaking any language other than English

and using all public transit (in fact, having a car would likely be very inconvenient). That makes it ideal to visit when you are on your own and using public transit / walking. The core city of Vienna is extremely walkable, less than a 30 minute walk to cross the entire city.
I would highly recommend spending more time in two locations, rather than trying to check off more locations by spending a day there. Every time you have to pack up, drive, find parking, and check back in to a different hotel, it pretty much takes up a whole day. You might get to see some countryside driving and find a cute restaurant for lunch, a nice dinner... but being able to see any "attractions" is limited. I base this on my experience when we drove from Budapest to Vienna, which was "only" a three hour drive, and several train rides in Europe where I thought, "Oh that will only take a couple of hours" and it ended up taking most of a day.
So I would say go to Tura Luka and Bratislava and explore Slovakia for a week, while you have a car and an almost-local with you. Or a trip to Prague and Czechia where you explore some outlying regions would also be nice.
Save Vienna and Salzburg for a later trip where you might not have those resources and don't have the hassle of parking a car you won't really need.
ETA: I just saw you will have many European languages in the group (a huge plus for exploring smaller places) and also that it's a large-ish group. Which makes my "Any day of travel will take up a full day" even more likely. Focus on fewer locations.
Also, there are great wines in Hungary - pick the Hungarians' brains about that. They have some really unique varietals that aren't exported at all.