any alternatives to Kings Theatre?
Leamington Terrace (although it has its own gradient problem), then Leamington Walk, Middle Meadow Walk.
How do you do the Innocent to Parliament?
Rankeillor St, St Leonard's Lane, St Leonard's Hill, Braidwood Gate, Dumbiedykes Road, cut through into Holyrood Park before the play park. There are some steps and missing dropped kerbs, but it is a very quiet route. Braidwood Gate is fairly steep as well.
Alternatively:
Rankeillor, Hermit's Croft, East Parkside, Holyrood Park Road, then onto the paths through the park (not sure about legality of cycling on the paths between Holyrood Park Road and the northernmost roundabout). Longer, but steadier gradient may make it preferable on the way back?