switzerland - austria - germany trip

Even skipping the black forest (which I recommend skipping), it'll be a lot of time in the car. Just do the Zurich, Innsbruck, Garmisch, Dornbirn, Zurich loop, that's all you have time for. A comment about the Zurich to Innsbruck route, google may say 3 hours, but we've found it always takes longer (1-2 hrs longer), especially in winter. There's a series of full and partially open tunnels on narrowed roads which makes for unpleasant driving.

If you've not booked your flight, try flying into and out of Munich. It's easier to get to the areas you're showing interest in and is a great airport. The Munich-Salzburg-Innsbruck--Garmisch--Fussen--Munich circle is just more efficient in every way. Also, try to grab another 2-3 days, as 5 days is very short for this region. Zurich is not in the mountains, and I've found the Black Forest doesn't have the incredible Alpine scenery of Tirol and Austria.
And Munich has so many more travel sights to see.

Seems fine to me but I have idea about your kids. You know better than we do how they react to being strapped in, and you know how old they are.

If all you have is 5 days then I think you will be spending most of your time driving from place to place and not enough time to visit in each town. I am assuming that you want to see different sights at each town that you mentioned. With kids you have to plan for things not flowing smoothly. Good luck.

It would be a nice 10-14 day loop, but not much fun in only 5 days.

Innsbruck and Garmisch (just for instance) have swell cable-car rides with soft hiking at the top that you could spend most of daylight on. The Black Forest is attractive in season, with even softer hiking available. But the roads are curvy and narrow, if two-lane. You can't set off from Triberg, you have to get there first! Despite the Google timing, I'd allow at least three hours for Triberg-Zurich, with only bathroom stops. And you didn't mention stopping at the Rheinfall, Lake Konstanz, Stein Am Rhein, or Winterthur. Take the previous advice.

Unfortunately, my number of days are set. Hence, I am not covering Rheinfalls etc.
Looks like I have to moderate the program a bit..

Thanks to all who replied. I actually enjoyed the trip quite a bit with the itinerary as detailed above.