Itinerary help & transportation suggestions for large multi-generational family

We have 9 days which I know is ambitious

Sorry to say but it is unrealistic. All your mentioned places have very much depth, means lots of attractions and interesting points to stay. So, time to do some priorities.

• Take the fast train axis Berlin, Nuremberg, Munich as a real valid opportunity to travel along plus maybe a day trip to Neuschwanstein. This already fills up your itinerary. For Berlin you will need 3-4 (normally 4-5) days, Munich 2-3 days, Nuremberg 1-2 days plus all the transport in between.
• I know that RS readers are very much focussed on Black Forest but there are alternatives that are not so far out of your way: Saxon Switzerland, Harz, Ore Mountains, Fichtel Mountains; just to name a few.
• Rhine Valley is beautiful but how shall this fit in these 9 days if you look onto a map? Travel-to takes a day plus 1-2 days to explore. Alternatives: UNESCO world heritage listed palaces in Potsdam (near Berlin), the Imperial Caste in Nuremberg, red fortress Zitadelle Spandau (Berlin) and some others.

I do not want to spoil your pleasure but I think that you will have a real better experience with seeing quality instead of quantity. Also size of group and needs of kids and toddler play a role.

This is way, way too much for 9 days, especially with the children. Pick 2 cities, tops and day trip from those, though 1 city only is going to be better.
You say 9 days, but does this include your arrival and departure days? If so, just stay in Munich for those 7 days you have for sightseeing. Day trip to Salzburg, Regensburg, Oberammergau, Garmisch, etc.

The best cruise on the Rhine is from Rüdesheim to St. Goar, not just from Bacharach. This cruise does not fit into your travel plans very well though.

The Black Forest is not that special and does not fit into your travel plans either.

Look for Ferien Wohnungen or perhaps a Bauernhof (Farm stay) for a family of this size.

Also, if anyone can help with suggestions on how we can all get around since we need to all travel together in one big group.

Planning a feasible itinerary - and physically moving a group of 13 from city to city with luggage, purses, toddler bags, etc. - that would be a bold and difficult undertaking with a group this size. So I suggest you move everyone and their stuff only twice - once from your arrival airport to your rental home, and once from your rental home to your departure airport. As Jo suggested - ONE travel base, with one "home" for the duration of your stay, is the best way to do this. When you leave your rental, your bags stay home. If it's a GOOD travel base, you will be able to make day trips without all your stuff to many nice destinations.

You won't be able to do your whole wish list. That said, your wish list seems to mirror Rick Steves' suggestions for seeing Germany, which may or may not be the ideal itinerary for everyone. I'm trying to imagine a group of 13 with oldsters and little kids getting around Berlin on the U-Bahn... So I just want to assure you that in Germany, it is no sin to cover less ground than Rick suggests. If you keep a smaller travel circle you will not only endure less hassle - you will likely see more and experience more as well.

The best overall one-base town I see on your list is NUREMBERG. I would attempt to find adjacent rental apartments (or a large home) there. Nuremberg's advantages:

• Direct train access from FRA airport (with bags, avoid a change of trains if possible.)

• Close enough for a day trip to Munich - and many other easy day trip destinations are nearby: Würzburg - Bamberg - the Open-Air Museum in Bad Windsheim - Rothenburg - Iphofen From a Nuremberg base you can decide as you go which places you will visit and on which days. The VGN Nuremberg transit authority provides cheap day passes for group train travel to these and other places (use Bayern Ticket day passes for Munich.)

• An attractive, mostly walkable old-town center with a large zone for pedestrians only; many museums, WW II history, the Imperial Castle (previously mentioned,) local/regional specialties - in other words, a one-place stop that offers easy access to SOME of things that might otherwise draw you to Berlin, Neuschwanstein (which is NOT a genuine castle) and other distant places.

The Middle Rhine Valley ("Bacharach" on your list) is not very far from FRA airport. It is a wonderful place that everyone seems to like, and I feel really bad about leaving it out of the above-suggested plans. So... if FRA airport will be your departure point, I suggest that you leave 2 nights at the end of your Germany stay for a short stay near the airport. FRANKFURT - or better yet MAINZ - would be logical. MAINZ puts you on the Rhine and closer to the scenic part. Let's say you have 9 nights altogether... On the afternoon of day 8, take the train to Mainz and arrive in the evening. Leave bags in your rooms on Day 9; take the train to Bingen, do a cruise, touring a Rhine castle, and visiting Bacharach and another town or two, then return to Mainz for your final night. On Day 10, catch a direct train from Mainz to FRA airport (25 minutes.)

Note that there are special advance fare deals on German railways for large groups - see here

Thank you for the great feedback! I did mirror a large portion of the trip itinerary above based on Rick Steve's itinerary just taking out the locations we wanted to bypass to save days but it seems the logistics of movement & transportation may be too much to overcome for our large group. Thank you for the reality check lol Going to go back to the group to discuss :)

I would definitely cut out Berlin and save that for another trip as it is so far from the other places. Other than that, it is possibly doable, although you will be traveling so quickly you will not have much time to enjoy the places you visit. I would suggest travel by train, as you would need two vehicles for 13 people, and that would be difficult logistically. What is it you want to see in the Black Forest?