Trip to Germany in early Summer

What is the family make up? Numbers and ages?

Journey planner of Deutsche Bahn, it handles also size and ages of group:
https://int.bahn.de/en

Train stations in Germany - enter German names:
https://www.bahnhof.de/en

Station name of FRA airport for long distance trains:
Frankfurt am Main  ✈ Flughafen Fernbahnhof

In Frankfurt, you do not need to stay close to the main train station. There are trains every 15 min. from the city center, going out to the airport. Look for hotels near the Hauptwache. Flemings, Moxy, Motel One, or high end - Steigenberger or JW Mariott.

Sam, we are a family of three. Our son is 12.

Thank you in advance for any advice.

Welcome to the Forum, L.G.

I'm very curious about Frankfurt and Stuttgart (2 cities that get very little attention in Rick's materials and are somewhat unusual choices for first-time visitors to Germany.) Rick doesn't suggest Frankfurt unless you have 3+ weeks at his planning page and doesn't mention Stuttgart:

https://www.ricksteves.com/europe/germany/itinerary

I applaud itinerary plans that meet personal needs and interests, whether Rick likes them or not - just wondering - What moved you to choose these 2 cities?

I lived in Stuttgart for 9 months and it is not a great tourist city. It does have the Mercedes Factory and Porsche Factory.

Have you decided WHAT you will do in each city. TripAdvisor.com is a great source.

Strasbourg is fantastic. Also, the Black Forest is very nice. Consider Baden-Baden, Triberg and Titisee.
Also Heidelberg is worth an afternoon.

2 nights in each location isn’t much. If you don’t find enough to do in Stuttgart. ( I think thete is plenty for 2 days ), take a day trip to Tuebingen

In Stuttgart take your son to the Naturkundemuseum Stuttgart, Museum am Löwentor (not to be confused with the one at Schloss Rosenstein). It's one of the best dinosaur museums anywhere.

I can't advise on hotels in Frankfurt or Stuttgart, but in Strasbourg I have used the Maison Rouge which is right in the center of the old town and fantastic, and the Aloft which is a bit further out (but where I had parking). I'd use either again. I wouldn't stay right by the train stations.

One option you may consider is staying in Mainz instead of Frankfurt. It's very easy to catch a train from Mainz to the Frankfurt airport. There's one about every 15 minutes. Stay at the Hyatt Regency, it's right on the river.

Thanks Russ.

Not a lot of good options flying out of Boise -connections, fares- but Frankfurt being a main hub had the better ones. Stuttgart was an easy choice as our son is a car fanatic, so the Porsche and Mercedes Benz museums were a must.

Also wondered why this city wasn’t in any of Rick Steve’s guides.

I certainly applaud your children's getting input to the trip. (Ages?) You are traveling so far, and only for six nights "in country!" I like large cities, and I grew up in NYC. (That's also a reason I wouldn't cross the street to see an automotive museum! Neither of my parents ever owned a car in their lives. But on our sixth time in Germany, we did drive by a BMW factory, but just because it was designed by Zaha Hadid, a deceased star-chitect.)

We enjoyed Strasbourg, but that was during a trip solely to the French area of Alsace. I just wonder if your children wouldn't be bowled over by seeing Cologne for two nights, and the scenic Middle Rhine, by train and day-boat, maybe with Koblenz thrown in? No car rental needed, which I assume was your plan. I'm just trying to find a more distinctive second stop, unlike Stuttgart. Although Frankfurt has a (small) historic area, good museums, and a nice market-hall, it's a very commercial city. I just think that Frankfurt/Stuttgart is kind of like Chicago/Cleveland. (Lived in Cleveland 2 years. 3 visits Chicago)

With Porsche + MB and post-war Stuttgart as "musts", I suggest spending the remainder of your short time in Germany not in post-war Frankfurt but in some of the smaller old-world towns that are within easy reach of FRA airport. These places are within 1 hour from FRA airport by train.

Bacharach, in the UNESCO World Heritage Middle Rhine Valley:
https://www.mittelrheinentdecken.de/en/villages-towns-and-cities/bacharach/
Take a Rhine Valley river cruise past dozens of castles.

Eltville, on the opposite riverbank:

https://www.tripadvisor.com/Attractions-g983854-Activities-oa0-Eltville_am_Rhein_Hesse.html

Oppenheim, Nierstein, Nackenheim, Bodenheim - the Rheinhessen Wine Towns, connected by train and by walking paths:

https://www.outdooractive.com/en/route/hiking-trail/rheinhessen/rheinterrassenweg-stage-oppenheim-nierstein-nackenheim-bodenheim/9379980/

I feel it would be amiss not to recommend the following place for you to take your son. While I love both the MBZ and Porsche museums, there's an even better museum just up the road in Sinsheim. The Technology Museum is heads and shoulders above the two car museums, even if they are combined. And if Sinsheim is awkward to get to, it's sister location in Speyer is easy to reach via the train.

Either location has more cars than the two car brand attractions and then you have aircraft, boats, submarines, spacecraft, military vehicles, automated music machines, carnival displays, trains, etc.

https://sinsheim.technik-museum.de/en/

I traveled with my son when he was 12. We visited 15 countries and nearly as many car museums. The Mercedes-Benz one was my favorite, hands-down. I didn't know about the one in Sinsheim mentioned by KGC, though.
There is also one in Mulhouse, France, which is a day trip option from Strasbourg. We didn't get to that one, either.