@Stellanotbud here is my definitive
guide to Munich Christmas Markets:
The Residenz - this is a massive palace which is v much worth seeing itself. In the front they hold a market based on crafts eg glass. Personally I thought this tended to the tat, but children will prob think it is magical. This is the place to get your Nurnberg sausages and Eierpunsch
The Medieval market - this was probably my favourite. Full of medieval style stuff eg axes, but a lot of fun. Main drink - Feuerzangenbowle
Marianplatz - this is basically huge and spreads out all down the main street as well. There are separate zones specializing in different things including an amazing and expensive Nativity section. There are lots of places selling Gluhwein in various flavours, lots of traditional Christmas market food. Personal fave drink - Luamba.
Viktualenmarkt - not actually a Christmas market but a huge food market. It's gorgeous all year round.
All of these are in walking distance of each other.
My other top tip if it is snowing would be going to the Nymphenburg Palace. It's not far on the tram. The Palace itself is gorgeous but in the snow walking around the grounds and seeing all the random and over the top small buildings in the gardens is great.
There are various other Christmas markets spread all round the city which honestly I wouldn't bother with. I have v bitter memories of walking to the one in the Englischer Garten, freezing cold, and discovering it was pretty average. It is still our benchmark of how cold it is possible for a human to be.
Munich is also the home of world class opera and ballet. You can book the Bayerische Staats Oper on line - I'd be surprised if they aren't doing the Nutcracker and/or Hansel and Gretel (personally think Hansel and Gretel is more magical). Warning - opera is really popular in Germany so book early.
The other opera house is Gaertnerplatz - this is a bit cheaper but also v high standards. They are more likely to do operetta and musicals alongside more popular operas and ballets. Given you can't really see operetta in the UK, and it is much more approachable than a lot of operas this is worth a shout. They will certainly have a fun Christmas show.
The centre of Munich is really easy to walk around, all the museums are in the centre as well. You could easily pack a lot into 2-3 days.