Three days in Scotland with my 12 year old son

Instead of the train to Edinburgh, you could fly from London to Inverness or Aberdeen. Or take the sleeper train:
https://www.seat61.com/sleeper-to-scotland.htm#trains
But I think you need to save the Highlands for another trip. You have plenty to do in and around Edinburgh to occupy your 3 days (and 4 nights? or 2 days and 3 nights?). You can also take a train directly from London to Stirling now.
The Kelpies and the Falkirk Wheel are very impressive. I know my son would have loved seeing them when he was 12.
Here is a day tour that will take you to Stirling Castle and Kelpies (but not the Falkirk Wheel):
https://www.rabbies.com/en-us/tour/loch-lomond-national-park-stirling-castle-day-tour-from-edinburgh?_gl=1*1l6l75k*_up*MQ..*_ga*MTEyNjk4MDIyMi4xNzkxOTAzMTg5*_ga_CQ6TXTDB4F*czE3OTE5MDMxODgkbzEkZzEkdDE3OTE5MDMxOTEkajU3JGwwJGgyMTc2MTM1Nzc.
Of course, Stirling is easily done on your own by public transport.

The Glencoe Mountain Resort does have Eco Lodges which you could stay in- they are pretty basic and functional, nothing at all fancy- https://www.glencoemountain.co.uk/accommodation/

You can catch an afternoon coach (bus) there direct from Edinburgh at 1400 (run by Ember), so that would enable you to wake up to a sunrise there, if the weather complied and was not wet and miserable- https://www.glencoemountain.co.uk/accommodation/

Then take an afternoon bus back to Edinburgh.

Alternatively Ember also run a bus at 0420 from Edinburgh, which arrives in Glencoe at 0700 which will be almost an hour before sunrise, have your hike (weather permitting) then the afternoon (1700) bus back. A pretty long day.

Depending how early you are arriving (the first Lumo train arrives at EDI at 0957, and the first LNER train at 1028, you could put your luggage in left luggage at Edinburgh Waverley and take the next train out to Stirling.

From the 0545 train (the 0957 arrival) you should be at Stirling by 1116, with 36 minutes at Edinburgh to go to left luggage.

Look at www.visitscotland.com for some great photos, and other great information on Castles, etc. IMO Glencoe is too far to go just to see a Mist in Late November with only 8 1/2 hours of Daylight? Visit Stirling Castle which is not that far from Glasgow and Edinburgh. Linthlingow is a beautiful relic palace, which was the birthplace of Mary Queen of Scots. The Kelvingrove Museum and Gallery is always reccomended to visit in Glasgow. Some faraway sites in Scotland start closing in October. Have fun!

Thanks for the info. Thought about the sleeper train but my boy is a very light sleeper and did not like that idea. Already have train tickets from KIngs cross to Edinburgh. But, your idea of flying into Inverness is a good one.

Hello, isn’t there a tour to go hiking in the highlands for a day? If not, you could do a bike tour to the Highlands for a day. Tartan bicycle company is fabulous and they offer one. Might not be the best time of year for it but maybe you get lucky with the weather. They also offer a tour that goes around Edinburgh which is a lot of fun and would let you see a lot of sights in the limited time you have.

I saw Inverary castle mentioned. Please note that it closes for the season on 26th October, and that closure is common for tourist places outwith the central belt.

That week in November sunset in Edinburgh is 1555 to 1600. Further north it will be earlier, it is also going to be very wet is the weather is per normal - memories of playing rugby at school in November flood back. November to February are very much 'indoors if wet' months for Scotland.

I would suggest focus on the Forth Valley area - Edinburgh to Stirling. If the Highlands are an essential remember so you can say you've been, the Highlands come in a lot closer to the central belt/lowlands than the administrative map suggests. Perth and Stirling are both 'gateway to the Highlands' cities, and the boundary runs through Glasgow's commuter belt.

That said, if you only have three days, Stirling and Edinburgh castles can easily fill most of one each. Of those I'd visit Stirling because of the views from it across the M9 and Bannockburn to the Highlands beyond.