I tried drove around 21 days in UK ONE of the stop is Edinburgh
Stayed for castle , Gordon Ramsay recommended restaurant and bought some wine and spirit mini bottles
I used to be there by train in London, coz I was return to London for sight seeing, but u could take Virgin airline to Edinburgh too, u would transit in London.
I was took CX to London first then transit in train to Edinburgh~ actually I think BA and VA is a good choice and a bit more space for the seat than CX~ and I would also concerned about the arrival time in UK
More information, I was booked my ticket at http://www.thetrainline.com/buytickets/ the price of the ticket is quite fluctuate~ should checked time on time~ but if u buy later then then ticket would become more expensive
As I think Edinburgh mainly for sightseeing but not much exciting things for kids~ if ur child love to seeing more natural scene then I think would be fine~ but I\'m not suggest u take ur son by train to be there, since 4-5 hours sitting on the train but nothing to do is quite boring~~