Afternoon Tea for famlies in London?

Since you've already done fancy why not opt for a themed tea? It seems like there are dozens to choose from around London. I attended a Charlie and the Chocolate Factory-themed tea at the Chesterfield Mayfair a couple of years ago that was delicious and while their theme has changed the quality of the food and friendly service likely have not. https://chesterfieldmayfair.com/dining-and-drinks/afternoon-tea

If you're interested in a small, but quaint Cafe vibe you could look into the English Rose Cafe and Tea Shop. We did a full afternoon tea there in April and went back from a cream tea later in the trip because we enjoyed it so much.
It's affordable and the scones are top notch 👌

Bea's of Bloomsbury, any of their locations.
Excellent tea and cakes and it won't break the bank.

hey hey shea_lewis
afternoonteaonline.co.uk
chose london and see many tea rooms, cost, and what's offered.
b-bakery.com
bridgett's bakery has red double decker bus tours around main attractions of london, peppa pig bus tea party
bridget's bakery in covent gardens also has tea in their bakery
register at wowcher.co.uk, it's free. like groupon
under more click afternoon tea. many different places that are 2 for 1 specials
stmartin-in-the-fields.org
click visit, scroll down to afternoon tea. cafe in the crypt
podiumrestaurant.com/ childrens afternoon tea
thedillylondon.com/ peter rabbit afternoon tea
egertonhousehotel.com/ afternoon tea party (princess and prince party)
don't know ages of your kids and how long kids have an attention span, picky eaters, getting tired and bored of churches, museums, etc.
have a great time and enjoy.
aloha