Don't know what funds are like in the Fearnhead household (although living 2 seconds away I suppose I could guess!)
For safety and piece of mind a taxi to stadium from Picadilly will be a 5er. That will save her little legs before the standing around waiting for the show to start.
After the show there will be literally 100's of people walking back to there, so should be a lot safer then.
If you care not for the wife's safety, head out of picadilly station, down the approach, first right, follow that road down all the way, cross the dual carridge way, behind some new flats/retail park, take a right and keep walking. (And keep an eye eye for middle aged women in flashing bunny ears, if in doubt, follow them!!!)