Thank you all for your suggestions.
I am thinking proper afternoon tea - with the dainty sandwiches, cakes, pastries, scones etc But was really not sure on what the sandwiches should have in them, and which cakes/tarts etc would be most English.
Drinks were confusing me too, as I can imagine the horror some of them will feel when their tea comes hot in a tea cup, rather than in a glass clinking with ice and know I have to offer something else!
So...
Sandwiches:
Cucumber
Smoked salmon, cream cheese and dill
Egg mayo and cress
Ham and mustard
Scones with cream and jam
Bakewell tarts
Chocolate eclairs
Shortbread
Full size cakes to slice:
Victoria Sponge
Carrot
Lemon Drizzle
Coffee (and Walnut?)
Battenburg
Also the birthday cake, which will be white chocolate sponge with raspberry jam done up as Thomas the Train.
Does that sound reasonable and thoroughly English? Maybe with another kind of pastry or biscuit thing or two?
In addition to inflicting hot tea on them, I'm thinking I am going to offer coffee, possibly a fruit punch and maybe proper Lemonade? DH will probably also dispense his homemade beer and gin and knock everyone out I could get some squash, but it is jolly expensive in the World foods aisle of my grocery store.