Family of 4 in 5 countries in 17 days - which hub cities?

Obviously with your passes the plan is to ride the rails considerably.
You will be limited with accommodation choices I expect at this late stage.
The route you suggest is basically sound with numerous day trip options from each place.
I would spend your first night in Switzerland at least...

Luzern, Switzerland - 1 night
Innsbruck, Austria - 3 nights (Salzburg & Munich)
Padova, Italy - 4 nights (Venice, Dolomites, Verona)
Nice, France - 3 nights (Antibes, Monaco)
Avignon, France - 3 nights (Nimes,Arles)
Barcelona - 3 nights

I have not been to the Italian Alps but from what I have read they are fantastic and worth a stop.

I lived in Augsburg, Germany for four years and have traveled extensively, visiting all the places you mentioned. Of course, I have my preferences, but I will try to assist.

Innsbruck is a beautiful city for a couple of days, you could visit, Garmisch, Germany from there. Neue castle is there. I think using Innsbruck to visit Munich and Salzburg is a bad idea. You will waste a lot of time traveling.

You may have boxed yourself in unnecessarily trying to find a hotel room for four persons. Many European hotels just don't have such rooms. Still, some of the pricey hotels may offer that, but I suggest you look for two rooms at Bed and Breakfasts or smaller three star hotels. For hotels, Rick Steves website can help, also Kayak website.

Stopping in the Dolomites to hike is a personal preference, can't tell you if it is a good idea. The Alpine scenery is great, but then so is Venice, Rome, etc.

Venice, Rome and Florence are the big three in Italy and easily done via rail. Why do a day trip to Florence from Rome? Florence is on the way from Venice to Florence. There are so many places worth seeing in Umbria and Tuscany, it is hard to cull them down. I happen to love Siena. Pisa may be worth an afternoon to see the Sacred Compound.

Cinque Terre (one or two days) can probably be done by rail, but have to check the schedule. Clearly, you need to do some serious planning. Have you purchased any Rick Steves guides for Italy, France, etc?

Southern France is full of great places, but many of the great places would require an auto or to be on a tour. They are not on the main rail line.

Monaco, Cannes and Nice are worth a visit, but I just love Avignon, St. Paul de Venice and some of the out of the way places. Arles is good as well, but you only have 17 days and after visiting Bavaria, Austria and Italy, you may be a bit short. Barcelona is a nice city, but compared to Rome, Florence, Venice, and others, plan on a couple of days there at most.

Thank you for feedback, this community is great, I should have reached out long ago! The arrival/departure cities were dictated by availability using miles on United. The bright side of my procrastination is that we are fluid and can make changes. I planned to order Global Passes today (expedited), but now rethinking, bu 4 country passes are not much cheaper. Maybe a car for the north is a better idea giving us freedom to see multiple cities/sites and stay in out of the way inns with better availability, then switch to rail through Italy? Perhaps a car in So France is also better, we can pick up car in Nice and see Avignon, etc., drop car in France, then back on rail to Barcelona? It does sound like 2 days in Barcelona may be enough so we can add some time in southern France. For Italy, does it make sense to have a hub city with day trips by rail? Thanks again for your help.

right then. Time to get out the rational stick and have a look at it.

You already know that the trip you outlined is looney toons - too much to do in too short a time stopping too much. Let me validate that thought. It is too much.

So what to do?

Do any two of you, preferably the adults, agree on where to go? If you could not agree on the destinations so are trying to please everybody and going everywhere, I believe that you will end up pleasing nobody.

Surely that is not why you scrimped and saved and dreamed of a lovely family trip to Europe. Somebody has to (wo)man up and take the reins and organise something that everybody will enjoy, even if nobody gets exactly what they hoped for.

How old are these teenagers? Big kids or little adults? 12, 13, 14 is a lot different to 18, 19. Can they help plan now that school's out, if given sufficient direction and guidance?

17 days (including arrival and departure days, which don't count in my book) is a fair amount of time to see quite a lot, but if you are not organised it pass in a flash.

You need to cut. Go to one of each kind of place, and really enjoy each place. Give the kids something interesting to do in each place, like learning to row their own boat on the canals of Venice and summer tobogganing (Sommerrodelbahn) down the mountains and hills of Switzerland, Germany and Austria. By the way, these are fun for parents, too. But if you are zooming through Europe at full blast you will miss them. Your plan is to go to Venice and only spend part of one day there? An absolutely unique place?

It sounds like you want Alps, and have Switzerland, Austria, Germany and Italy in there, but don't intend to see Switzerland (and its incredible full scale sized rain layout and magnificent Alps) at all, nor Germany. I think you have an awful lot of duplication in there.

By Neuf. castle what do you mean? Are you talking about Neuschwanstein, the 19th century non-castle, from which Disney modelled his magic castle, or do you mean something else?

You are talking about driving to whichever castle that is yet you are paying for a train pass?

You would do far better to fly - if any cheap flights are still available (or is cheap less important than convenient?) - from Italy to Spain.

I'm cutting to the bone here and asking a lot of questions because of your lack of planning and the fact that your trip starts in a couple of weeks, so we only have a couple of days to try to straighten this out so all 4 of you go home happy.

Help us help you.

Can you get to Larkspur on Saturday? Lots of well experienced folk who can help you face to face at the monthly meeting of the Bay Area travel group. See https://community.ricksteves.com/travel-forum/travel-meetings/sf-bay-area-travel-meeting

Renting a car has its advantages, but disadvantages. First, if you have a smart phone with a chip that works in Europe or have a GPS, you need that. Also, renting a car in one country and dropping in another can incur some steep costs. Cars are great for seeing small cities, towns and countryside, but if you focus on big cities, rail is better.

Also, if you rent a car, make sure all your luggage fits in the trunk. Going into Italy, if you leave stuff in the car, visible your car may be broken into. Some advise if you leave stuff in the car that is not so valuable, leave the car unlocked so no one breaks a window to get inside.

Skip the rail pass, individual tickets may be cheaper? I think you need to pare things down a bit as well, my thoughts...
Luzern, Switzerland - 2 nights
Innsbruck, Austria - 3 nights (Salzburg & Munich)
Padova, Italy -3 nights (Venice, Dolomites, Verona)
Lucca - 4-5 nights ( Florence,C.T. Pisa)
Rome-3 nights FLY to Barcelona, it's only $40 on Ryanair
Barcelona - 2 nights

I have never traveled this route and am looking for the experts to comment and tweek if need be.
Have a great time!

The south of France doesn't sound like your highest priority. Flying from Rome or Pisa to Barcelona strikes off a lot of time and money "at one blow".

If you did choose a rail pass for travel through France, then I'd advise you to book the French TGV train reservations in the same booking, to be sure of availability. In Switzerland, Austria, and Germany, your trains don't require seat reservations, but in Italy you'll add on €10 per person for fast trains.

Rick’s Train Travel Time & cost Map gives you an overview of faster train travel times in hours and regular (full-price) 2nd-class ticket prices to buy as you go. If there's any long train ride that you're ready to book during the planning stage, then you still might get some advance discount on those tickets.

Rick's hotel listings are in his guidebooks, not on this site, with quads and family rooms listed in most cities. I see a lot of quads among his Rome listings, for instance, but confirm the specific bed layout when reserving. A site like booking.com also makes it easier to see current availability when supply starts to fill up.

I think a lot of hotels can accommodate 4 people. Also consider renting two rooms. That way you also get two bathrooms, which while more expensive, can make the trip a lot for enjoyable for everyone.

You may need a mix of train, plane and car to maximise what you want to achieve.
Maybe start off by locking in some point to point journeys by rail.
Luzern (2)
Innsbruck (2)
Salzburg (2)
Munich (3)
Fly from Munich to Pisa/Florence/Bologna.
Base yourself for 5 nights, hiring a car.
Fly from Pisa/Florence/Bologna to Barcelona for your final 3 nights.

Amsterdam and Budapest would be my two hub cities. You can reach most of the free world from these 2 locations.

Have you looked at a map to see the distances, and time, you will spend traveling from one place to another? One day in a place is really only a few hours, considering the time it takes to get there and back. Also, consider the time it may take for 4 people to pack up and get ready!

I completely agree with those that say you have way too many stops. Since you have 4 people, why not each one pick one place, and stay 3-4 nights, and do shorter day trips.