Minimal cooking absolutely! The supermarkets all sell haggis. Get a Macsween haggis. Wrap in foil and place in ovenproof dish for an hour at 180 C. Then remove the skin and eat. It's that simple. While the haggis is cooking you can bake a couple of jacket potatoes alongside which goes really well with it.
At the Farmers market you can buy all manner of foods that will just need heating up eg cullen skink soup, great cheese and breads, pork pies etc.
If you like your morning porridge, don't miss the Stoats porridge stall with toppings like raspberry and cream or white chocolate and hazelnut.
We were recently in Edinburgh. Not sure if you are self catering but if you are let me know and I will fill you in re cooking haggis in your own apartment. We had a wonderful cullen skink from Creelers that have a stall at the Edinburgh Food Market as well as a bistro in town. www.creelers.co.uk.
The Edinburgh Food market is a highlight of the city and is open on Saturday mornings. Really not trying to push my own post here but if you want to read about it you can at kitchenjourneys.net/2012/10/edinburgh-farmers-market/ You can get great value at lunchtime even in posh restaurants such as Castle Terrace and Wedgewood both of which use Scottish ingredients. Also The Grainstore on Victoria Street has lunchtime special menues. A lot of places sell haggis adapted to other cuisines such as haggis panini, haggis sauce with pork baps (at Oink at the food market), haggis pakora, haggis with couscous. Just about everything except haggis sushi. There is a wonderful fudge shop on Canongate called The fudge House www.fudgehouse.co.uk
One specialty of the city that is less cuisine than carbs is deep fried mars bar. My son loved it - we got it at The Clam Shell fish and chip shop at 148 High Street.Once again - apologies - but you can read about this wierd experience at kitchenjourneys.net/2012/10/a-tale-of-two-cities/
Let me know if you would like some tips on museums that kids will love - we visited quite a few. Hope you have a great trip.
By the way if you are going to the Castle, they have a tearoom alongside the Royal Apartments that does a really good Scottish shortbread. Great with a pot of tea which you will need by the time you get to that part of the castle experience.