Edinburgh

I imagine the best time to visit Edinburgh would be on Sunday when Papi can come with us. One can take the Scotrail train from the Queen Street station at 9:30 am and get into Edinburgh's Waverly Station at 10:28. I'm not sure what the fare would be since they have a variety of ticket types.
edinburgh.org, the official tourist website, says the Edinburgh Art Festival runs from the 5th of August to the 5th of September and the Edinburgh International Book Festival runs from the 15th to the 31st of August. They say Edinburgh is hopping in August and hard to get a room in. And the Edinburgh Military Tatoo festival runs from August 7-29th. I'm thinking now maybe we DON'T want to go on a Sunday! Then there is the Fringe Festival (initially those who weren't selected for the Art Festival) from the 7th to the 31st of August.
They say a must see is the Edinburgh Castle but I think I'd rather spend the 13 pound admission ($21.50) on dinner instead. Although for "Concessions" (aged 60 and over) is only 10.50 ($17.40). I wonder if foreigners qualify for concessions.
I'd like to go to the Royal Botanic Garden but there probably won't be time. I think just wandering around the old town, having lunch in a pub and maybe going to the National Galleries of Scotland should fill up a day. They have an exhibit on Spain: From Goya to Picasso that we might enjoy, except that it has an admission fee of 8 pounds...