Frankfurt and Garmisch, how to do it

There are beautiful, residential neighborhoods in Frankfurt, like Westend, Nordend, or Sachsenhausen, but also lovely small towns surrounding the city. Try Bad Homburg or Kronberg. The Christmas market in Bad Homburg, held on weekends, is one of my favorites. Has the most hand-made Items I have seen at a market.

Check Wiesbaden Military Lodge and do daytour from there to Rüdesheim,Bacharach etc and the Rhine Valley

https://www.tripadvisor.com/ShowUserReviews-g187346-d3150837-r444799210-Wiesbaden_Lodge-Wiesbaden_Hesse.html

If you stay at the Edelweiss in G-P you'll have a good base for Austria, Bavaria, and Switzerland. I've used it several times when showing family around. But remember, in December it will be very popular as it's a base for the Christmas markets and for skiing. The Christmas time slots this past DEC sold out in 48 hours.

What I do with visitors, especially those who have not been to Germany, is base a couple nights out of Nuremberg before heading south. But again, in DEC this is a problem as Nuremberg will sell out, at high prices, due to the Christmas markets there. You will have the same problem in Wurzburg, Bamberg, Bayreuth, and most of the other cities in Frankonia.

Suggest flying into Munich instead of Frankfurt. Far more to see in Bavaria.
Garmisch is great, consider staying at the Fraunforfer Guesthouse and going up to the top of the Zugspitze.

uwe04 suggests a day tour "to Rüdesheim,Bacharach etc and the Rhine Valley", which I think is more than a day trip - this part of the Rhine north of Wiesbaden represents your best bet for a non-city area to base yourselves in for a week. Unlike Wiesbaden, these two old-world towns lie within the "Rhine Gorge" a 40-mile section of the river with dramatic cliffsides dotted with vineyards, castles, and other old-world towns. The Rhine Gorge towns are all well connected. Passenger trains on BOTH sides of the river serve every town between Koblenz in the north (where the two railways meet) and Bingen (or Rüdesheim, on the opposite river bank) in the south.

THIS MAP shows the Rhine Gorge railways, ferry crossings, and more.

We will be flying in to Frankfurt

FRA airport is well connected to the Rhine Gorge. THIS AREA MAP shows the railways in the wider area, with the Rhine gorge towns of Boppard, St Goar and Oberwesel, just north of Bacharach, all on the same train line. FRA airport (Flug.) and nearby cities like Cologne (Köln) Mainz and Frankfurt are also shown. With direct trains from FRA airport to Bacharach and Oberwesel (1 hour or less) as well as Boppard (just over 1 hour,) you should have no trouble with arrival and no troubles reaching Garmisch later on.

For "day trips using the train or bus", this area is ideal. And the ferry crossings run all day long if/when you wish to cross. You will also want to take advantage of a day cruise boat at some point; it's a fine way to take in the scenery in slow motion. Some of the castles (see this map) are accessible to visitors; Marksburg in the lovely half-timbered town of Braubach (near Koblenz) is tops. Chairlift rides in Boppard and in Rüdesheim will get you to the clifftops for views - and maybe for some refreshments along with the views, like these from above Boppard - or for hiking, which is very popular here as the views from the clifftops are awesome (here is a view from one of the trailside inns near St Goar.) Cologne, Koblenz, Wiesbaden and Mainz are nearby cities that can be reached for visiting museums and churches, etc,, although several of the Rhine Gorge towns themselves have interesting small museums and some fine churches worth visiting as well. REMAGEN, a nice town north of Koblenz, has an interesting WW II Museum as well.

Where to stay:

The Untours company provides stays just like the one you have in mind... one week in a small Rhine Gorge town with outings by train. You don't need to buy their tour- but their tour accommodations will give you an idea of the charming accommodations that are available in the Rhine towns. (The town names are not provided in the link above; the "Fairytale House" is definitely in Bacharach, however, as it's right beside the Steeger Tower.) I would look first at places on the west ("left") Rhine bank: Boppard, Oberwesel and Bacharach, with direct trains to/from FRA, would be my first choices. Boppard is the largest of the small towns and will provide the widest choices for dining and lodging.

I was surprised to come across this place in Bacharach which houses up to 16 people. How big is your group?

Edit: The owner (Stiehl) appears to have multiple properties there; the above apartment is the last of four on his homepage:

https://fewo-stiehl.de/

There will be seven of us. Great ideas, thank you!

I have never stayed at the AFRC Edelweiss Lodge. If they are anything like the old Patton Inn and they offer side tours it might be your best bet without a van/cars. I would encourage you to spend as much time as possible on the economy. Get the culture. Go out for dinner. Nowadays I stay in German, Austrian, hotels Gasthaus, FEWO etc. From Garmisch I point to Ehrwald Austria mostly for the scenery. I like to walk across the golf course there and visit the Ehrwalder Alm. Mittenwald, Germany is also close and a little further Seefeld in Tirol, Austria. If you are up to a longer day you could make the trip to Innsbruck, Austria.

I have stayed at the Edelweiss. Beautiful hotel, with lots of tour offerings, but the food is way overpriced and not that delicious. Go to other restaurants in town to eat.

We will definitely support the areas we visit! (Go out to eat, etc). It does look like we're too late to stay at the Edelweiss, but I've got an apartment tagged for the area. I've been eyeballing Bacharach for our stay up by Frankfurt (thanks to the person who suggested it!) My husband was stationed in Baumholder for 3 years and would really like to pop back in for a day. Its not far from Bacharach. My son spent 5 weeks in Garmisch for school about a year and a half ago. Now to decide rail vs car rental. I was leaning towards rail, but car rental (two cars) may be cheaper and more time effective.......

If you can add the https://www.partnachklamm.de/en to your list in Garmish. We took the bus from the train station. After that it’s a beautiful walk past the Winter Olympic Stadium along the river. Good for all ages (we are 69 & 63). It was a highlight of our trip and the only day it snowed. Was there mid-December.

There's not a lot of military left in Baumholder. Some small units mostly. You probably won't be allowed access, though you can check. Cars are handy if you want to get off the main roads, but if you're just planning on moving from one base to another trains are very practical.