Christmassy Day trip to London

[GirlsonFilm]

We're going to be in London for the day on 20th December and I want to give my dcs (6&8) a festive day in central London. I don't know much about the Christmas experience at Hyde Park but am thinking about lights in Regent's St, perhaps a show (Christmas or panto) and perhaps tea at Harrods ice cream parlour....but any suggestions or ideas welcome.

From north of the river you can walk over Westminster Bridge by Big Ben, or over the pedestrian bridges behind Charing Cross Station (by Trafalgar Square) as well as Waterloo Bridge.

To be honest central London is all very walkable, if you know where you are going!!
You could also get on the Thames clipper and for a couple of pounds each go across the river which is lovely!