3 hours in central London with my 7-year-old.. what to do?

Taking my daughter to see the Matilda musical on Saturday.
Will be staying Friday night at my aunt's flat in Deptford.
The show starts at 2:30 in Covent Garden and we'll probably head to central London just before midday.
Is there anything I should definitely take her to? Was thinking the National Portrait Gallery but not sure it will hold her attention for all that long.
Anyway, please let me know if you have any incredible suggestions :-)
Cheers!

https://www.somersethouse.org.uk/whats-on/beano-art-of-breaking-the-rules

https://novelty-automation.com/

Love that place

If weather's OK what about walk along Southbank and across Millennium Bridge?
Could take river boat up Thames from Deptford too.
My young uns loved the Tate Gallery big slope - just climbing it and running up and down and inside is fun too.
Is there a Xmas fair type thing there now too by National Theatre?
Pretty sure there's some kind of stalls in Traflagar Square also

Walk along the SouthBank, usually a crazy bubble guy outside the Tate Modern

Given you're in Deptford, I'd walk/bus down the road to Greenwich & check out the Cutty Sark (ship - who doesn't like 'em?).
Then you can train/riverboat it into town for the other stuff people have suggested.

Was going to be my recommendation too

London Transport Museum in Covent Garden is also good fun.

Bear in mind you will need to prebook for most Museums and attractions at the moment, even for free entry places.

Coram's Fields is nice too https://www.coramsfields.org/

Bodeans and gelupo?

Ooh yes.

We took the kids here and my suggestion on my birthday. Open air picnic at the Brunswick centre with Waitrose food.

Ain't no party like a doubleodavey party, that's for sure

Nice shop in Brewer Street I think (also understand that this may not help)

Hamleys toy shop, but seeing London from the river is a great idea.

Walk up to Hamleys from Piccadilly tube and she’ll remember it when she’s old.

Skygarden is good with free entry but booking required. Its in the walkie talkie building a few stops down on the district line from temple station

Get in to a fight with a swan in Green Park.