As you've been to Edinburgh before, you'll know what a hilly, cobbley city we have

probably wise you're doing it whilst your little one is still at buggy age!
As others have said, the museum on Chambers St is great, with plenty of interactive stuff and an AWESOME animal gallery with life size sculptures.
I would personally never recommend Edinburgh Zoo, sorry to PPs. It's common opinion locally that it's very cruelly led, and it is just heartbreaking to see some of the animals in there. The enclosures are quite small and the psychological damage is pretty evident in most cases.
Gorgie City Farm is great, though. There are pigs, goats, sheep, a cow, chickens and various smaller animals and reptiles (I think), it's great for little ones and DS had an absolutely great time there for his 1st birthday. It's free, and the animals are clearly very well looked after.
There's quite a few soft plays around Edinburgh if you get a rainy day or your little one needs to run off some energy. If you don't fancy one of the really big ones there's a few smaller more boutiquey ones with really nice cafes etc, two in particular that spring to mind are in Barnton and Morningside if you Google that.
If you get a nice day there's some good parks with playgrounds, and The Botanics. I've not been to the Commonwealth Pool in ages, but it's had a massive refurb in the last few years and I gather the family changing facilities are really good, and there is baby pool, soft play, creche etc.
If there is anything more specific that you want to know or want any help with accommodation (I run a holiday let company), feel free to drop me a pm
