How long are you in London for? Just the day right? Below is a list of places you could try but it is easy to incorporate some of this stuff by location. For example - I would group afternoon tea and V&A together as the best places are central.
Kona at the St James Hotel https://www.stjamescourthotel.co.uk/pdf/Menus/Afternoon-Tea-at-Taj-London.pdf have a variety of Afternoon Teas at different price points - I have been and enjoyed it.
If you want to splurge, The Goring does a very good one but it is quite pricey.
I would suggest breakfast and a wander in Brick Lane then The Armoury, then lunch either around there or St Katharine Docks then V&A and then afternoon tea. Have a bit of a break as Afternoon Tea is filling then maybe grab a late dinner at one of the suggested places.
Curries and Brick Lane
Personally I’d avoid Tayyabs - scanty portions, overpriced and mildly spiced for what it is. Needoo, which is almost across the road, used to be far superior (and I imagine still is for lamb chops and sheekh kebabs).
Dishoom is decent, its like hipster curry and quite fun inside.
Amar Goan is another place I would try on Brick Lane for seriously traditional homestyle Sylheti cuisine which you are unlikely to get in SF - spicy curries and lots of fish - not for everyone due to some very strong flavours but their rice, dal, keski and green beans and prawn is real comfort food for me. I prefer it to the other Sylheti place Gram Bangla, of which plenty has been written about before on Chowhound. Other, better, South Asian options are around Upton Park and East Ham tube stops where aren’t that far from Wapping but it really depends on how far you’d want to travel.
HOWEVER if you are in London on a Sunday then Brick Lane comes alive - there is loads of street food to choose from plus a fun market with clothes and old music / antiques and independent designers which teenager would probably enjoy. It’s quite a fun experience as a tourist.
Fish and Chips
Poppies, around Spitalfields is popular for fish and chips - also the Golden Hind in Marylebone.
For a pub experience you could do a lot worse than staying around East London again. Bacchus Sundays (http://www.bacchussundays.net/where-are-we) have a list of pubs where they do a truly amazing Sunday Roast. They operate in Shoreditch and Bethnal Green, amongst others.
Alternatively, The Grapes, in the docklands, near Wapping, is quirky and steeped in history - worth checking out for a drink.
For pizza and burger for teenager - you Franco Manca and Pizza Pilgrims which have a lot of branches are both decent and cheap.
Emilia’s in St Katharine Docks is great for Italian, another foolproof one for teenager. Solid and cheap homemade pasta dishes in a picturesque location.