Trip With Friends over Winter

Just a thought, since 3 nights equals just 2 days in each city, why not just relax and enjoy those cities?
You’ll be taking so many trains why add more train travel or bus?
Except for Zurich, we’ve been to all those cities more than once and still find fun things to do each trip.

Some suggestions for Research:
Food tours
Cooking classes
Walking tours
Dance classes

For "fun and unique," I like to check Atlas Obscura.

I see you revised your Croatia trip. Another bit of advice is that you tend to get more assistance if you engage those trying to help. Since you said you have train passes and hotels, I won’t comment on the schedule any.

Dec 25: Train to Budapest, 3 nights (Dec 25–28)

• Markets will open about mid-day on the 25th so by the time the train arrives and you get checked in the markets should be waiting for you. But go here to see which are open: https://community.ricksteves.com/travel-forum/hungary/budapest-christmas-markets-d26f8ab1-2048-4160-bfb3-bf13b096683e
• Other activities open every day you are in town will be the bathhouses and the skating rink at City Park. Sunset will be at about 4pm so it’s a great time to see the lights.
• The Great Synagogue and I presume the others worth visiting will be closed the 25th but open the 26th until 2pm (Friday) and closed on the 27th (Saturday).
• What is open on the 26th will be hit and miss. Most of the museums will be closed.
• The 27th should be a normal tourist day with everything open.
• A list of whats open that I came across: https://budapestchristmas.com/opening-hours

Dec 28: To Prague (night EN Metropol on the 27th or day train on the 28th), 3 nights (Dec 28–31)

• I’m not a big fan of night trains (hard to sleep and I need a shower in the morning), but sure that’s an option. Day trains take 7 hours. For those check out RejioJet and MAV. But you said you have your rail passes so maybe it’s too late for that. If it were me, I would fly RyanAir non-stop starting at about $90 in 1:15 and save about 3 hours door to door.

To Prague (night EN Metropol on the 27th or day train on the 28th)

FYI, this train just sits in the station in Breclav for 6 hours from 11 pm to 5 am.

Sam, thats how you get sleep on a night train, you park it. But I will say that the prices are remarkably good (from MAV). Two folks for about $160. Sure thats about what a hotel room in Budapest (with a shower and a toilet) would cost but you do gain some time and you save maybe $60 as you arent buying train tickets + a hotel room. But I would still fly. Two very simple airports 30 minutes from town centers. The only drawback is cost maybe $300 for a couple vs $175 for the night train or $210 for the day train plus hotel (more or less).

And two lists for Budapest: https://www.budapestinfo.hu/en/10-winter-activities-in-budapest-for-christmas-and-new-year
https://budapest-travel-tips.com/top-10/top-10-things-do-winter-budapest/

The reason the Metropol sits in Breclav all night is that it is a multi-sector train as is common in Europe.

It has through cars for Warsaw which are shunted directly onto EN406 (from Munich) at Breclav, for Berlin shunted directly onto NJ456 (from Graz) at Breclav, then the Prague cars are attached to the front of a day train from Breclav to Prague IC576- it conveys a Czech restaurant car from Breclav.
So you end up ex Breclav with a single sleeper car, then two couchette cars, then a 1st class day car from Breclav, then the restaurant car, then five 2nd class day cars.

From Budapest it is 11 cars long- 3 cars for each destination (from front Berlin, Warsaw and Prague) then 2 day cars to Breclav only at the rear.