Need help with itinerary 6 days in Hamburg at Christmas

Hi - here are some thoughts:

Christmas Markets.
Hamburg has several, some close before the 23rd, some are open until the End of January. You should be able to go to one at least, especially if you arrive a few days before Christmas. If your kids are teenagers, keep in mind that the drinking age in Germany is lower, so they will be happy to partake in the mulled wine - and you all will need it - chances are the weather is rainy, windy and cold!

Mseums.
Hamburg has many great museums, perfect for a winter visit. It depends on your family’s interests.
Strongly recommend the Miniatur Wunderland. I have never seen so many adults in a state of absolute rapture as around the airport display in the wunderland. Make sure your camera batteries are charged. The challenge will be finding a time to go when it is not packed. It is open over the holidays - go early or late, on the 24th if you can, and get tickets in advance.
Kunsthalle and Deichtorhallen are big art museums. Don’t forget to look at the “Elphi”, the new concert hall (Elbphilharmonie) - maybe go to a concert there? (Don’t know how hard it would be to get tickets). There will also be free concerts in churches around Hamburg during this time.

Lübeck.
If the weather is nice, you could consider a day trip to Lübeck. By train 45minutes, about 40 euros for all on the Schleswig- Holstein ticket (or less, depending on the ages of your kids).

Hamburg card.
The card looks like a good deal, especially if you will be using public transportation. It might make sense though to first figure out what you want to see, because Museums are not expensive and often offer a reduced family entry fee.

I hope this is helpful.

You might consider a day trip to Lüneberg, perhaps 45 mins away by train. We thought it was one of the loveliest towns we have visited anywhere. Connections were not difficult. Our time in Hamburg was fairly limited, but we walked all over and visited the Miniatur wonderland. I was impressed with the orderly and well organized entry process (we just walked up, no advance tix). There was a snack area while waiting for our admission so it worked well. We spent about an hour and a half but spoke with many people who were there for the day....Some major aficionados out there! Safe travels.

I second the choice of Miniature World in the Hafen City. On a rainy day (when I visited) it can be packed with wall to wall people. You may have to wait 5 min to get near a display.
Tickets for 'Elphi' concerts are very tough to get - they get snapped up through the internet almost instantly. A lot of churches offer Christmas concerts (Bach, Handel) and organ recitals, some are free. Check the program for St Michaelis (Michel), St Petri or St Catherine's Church - all in downtown.