Weekend in Edinburgh

Craigmiller castle is great. Loved it. It was very quiet the day we were there. I would also suggest you plan on visiting Hollyrood which is located at the south end of the Royal Mile. It is fabulous and full of history. Hollyrood wasn't something that was high on our list but ended up being a favorite along with Craigmiller. While we enjoyed Edinburgh Castle as well the other two locations stand out to us now that we are home. As for the big castles Stirling Castle was our favorite. Whatever you do make sure to take some time to relax and explore. Edinburgh is a beautiful city.

It gets dark around 4-5 pm in winter in Edinburgh; and can be quite windy and bone chilling, even when the temp is well above freezing.
So not just the cold, but the wind as well.
i was a student there for many years, and still haven't warmed up! ;)
i always take warm clothes when I visit Edinburgh, even in summer!
I think you need a waterproof and wind resistant jacket, plus a hat and gloves, and a scarf to keep the chill out.
Your long undies are great, as you can wear them during the day, and to sleep in if you're cold.
Smart to stay in Edinburgh for both days.
It's a walkable city to see all the historic sites.

Since you're keen on Edinburgh Castle, find time to have a meal in the Tower Restaurant inside the National Museum. It has a fabulous view of the castle and the rest of the city's skyline. If you time it right, you can eat during sunset.

The National Museum and the National Gallery are the best price, free, though some exhibitions charge.

The Castle is under the auspices of Historic Scotland, as is the Palace of Holyroodhouse which might be worth considering adding to the trip. It is at the other end of the Royal Mile, just opposite the Parliament complex.

If you like history, be sure to set aside at least half a day at Edinburgh Castle. There are so many smaller museums inside that could easily take up an entire day, in addition to the actual structure itself. I was only able to spend 3/4 of a day in Edinburgh (8am to 5pm) and was only able to see Edinburgh Castle and walk down half of The Royal Mile using Rick Steve's Walk (I didn't have time to go inside any of the museums along the way, though I did enter St. Giles' cathedral and the old Parliament building). I didn't even have time to visit the New Town.

Your english is excellent, don't worry about it.

Temps of 2 - 6 degrees Celcius (you may have terrified our american friends!!!) are probable in December. Much depends on the wind. And not the way you think.

UK weather is affected by the Altantic Gulf stream which has warming effect in the west. If the wind is from the east side Edinburgh will be cold, if it's from the west it will be warmer - and bizarrely if it's a strong wind from the west/ south west it will get warmer than with no wind!! I've checked the records for christmas week last year. Early on 20th there was a wind from the north and it was -1 at dawn, but the wind turned to south and the temps rose to 9 by dusk. For the rest of the week it stuck in the south west with a light wind and bright conditions and the temps were from 2 in the night to 6 in the day. Then christmas day the wind became strong and by mid afternoon it was 14 degrees - which is what it is this evening under a cloudy sky with very little wind!!! Sundays forecast high is only 14 (dull, wet, calm). So the weather in December can be as warm as August - how does anyone pack for that?

Snow in the city is very unlikely for any length of time, if they have any in their ski resorts before christmas they will be lucky! To see it you'd need to go into the highlands, and to touch it you'd have to climb high. But December is a dark month, the week before christmas sunrise will be around 08:45 and sunset by 15:45. March would be lighter and warmer (based on same cloud and wind conditions).