France -Germany- Austria Itinerary Help!

Your young children might enjoy Neuschwanstein
Castle but we found it to be very touristy and crowded and regretted wasting the time and expense traveling there.

Since you will have to pass through Munich to get to Salzburg, and likely change trains there as well, you might shorten the ride by stopping in Munich first, Then go to Salzburg, then to Munich airport from Salzburg with a single train change at Munich Ost.

The train trip from Heidelberg is nearly 5 hours with 2 transfers

When do you plan to travel? Normally best connection is 3 hours. Did you check https://int.bahn.de/en/ with date selection?

What is pulling you to Heidelberg? It's a detour off the Strasbourg > Salzburg route. You wouldn't have much time there, perhaps that's the idea... So if you're simply looking for a pleasant place to break up your trip that will be less trouble, pick a place on the route. Esslingen might do it.

https://www.esslingen-info.com/en/discover

Sample schedule, random date in August...

Lv Strasbourg 8:45, ar Esslingen 10:34 (one change of train in Stuttgart)

Lv Esslingen 8:04, ar Salzburg 11:59 (direct)

For what it's worth... I look at dedicating a full day's outing to Neuschwanstein as a big waste of travel time. The transport time to the final bus stop approaches 5 hours for the round trip, even if you happen to be staying right next to Munich's main station. Then you have a 40-minute walk up to the entrance with a walk of similar length back to the bus stop. All this for an overcrowded 25-minute tour.

With your schedule fairly tight as it is, you could instead...

• Spend another night in SALZBURG and make a shorter day trip into the mountains of Berchtesgaden. Lake Koenigssee is fabulous - take a cruise across it. Take the Jennerbahn lift for views. See the train route below. There's also a direct bus (#840) which gets you there even quicker.

https://www.springl-leitenlehen.de/images/Karte-02.jpg

Maybe take a salt-mine tour:

https://www.salzbergwerk.de/en

• Alternatively, add time in Munich for a tour of Nymphenburg Palace(in Munich.) LOTS to see and do, and it's right there in Munich. And great for kids.

https://www.theworldisabook.com/16991/munich-with-kids-nymphenburg-palace/

Forget Heidelberg and Strasbourg. I like them, but you won't enjoy them much in August. And forget the train. You need to focus on Paris, Salzburg, and Munich. Do Paris. Then fly to Vienna, which will cost about $100/each and take just a few hours. Then spend some time there or go by train to Salzburg, either way it's better than trying to cover that distance by train alone. (I'd spend time in Vienna, it's got a lot more to do than Heidelberg and Strasbourg combined.) And from there it's an easy train ride into Munich. It's a local flight so it's a lot easier than your transatlantic one.