Hey (: I live in Edinburgh, so I can tell you some stuff about here, but I'm not so sure about Galsgow and Stirling, sorry. However, here in Edinburgh the main shopping street is Princes street, you should definitely go there! It has all the main shops, such as Topshop, River Island, H&M etc.. Then off Princes street there are streets that have smaller, more expensive shops, but you should have a look there too. There's also the St James Centre, and the Princes Mall in town, which are good for shopping. For sight seeing, you should go to Edinburgh Castle, the Scots monument (it's on Princes street, you'll see it if you go there, but you can go inside and climb to the top), camera obscura, dynamic earth, Edinburgh dungeons, Mary Kings Close (ghost tour in the underground vaults-it's so scary, but worth it! Lol), and the Royal Yacht Britania. Most of these are situated around about town (Princes Street) but the Britania is in Leith. You can get buses o different places in Edinburgh very easily though, so that not a problem. Oh, you could also go to the zoo lol. I can't think of any other places right now. But when you come in Summer time, the Edinburgh festival (fringe) will be on. There are lots of little stalls and street acts and shows on then, and it's really fun and there's just a really good atmosphere around about that time. You will see it if you are in town, there's no specific place but the Royal Mile has a lot of good stalls and street acts during the festival, so you should go there.
The nightlife here is good (apparently, I'm too young to go to clubs lol), bur I think they are rather strict and you will need ID to get in, so I'd say there is no point in trying. Same for the whiskey, you have to be 18 to legally drink here.
Hope this helps, and have fun when you come to Edinburgh! It's great! Lol (: