Decide how formal you want to be. It is your home and your rules and as it is friends, they will just be glad to see you. Informal: one or two big cakes - traditional favourites like Victoria Sandwich / Coffee and Walnut - or formal: as others have said go small - but you could make one cake batch of, say vanilla, then divvy it up and add some coffee / chocolate or cocoa powder to make 3 varieties.
If it were me, I would e a bit tongue in cheek (Sounds so clichéd, but I used to be a vicar's wife and loved having tea at four!) I would make dainty cucumber sandwiches - crusts off and drape them with a damp tea-towel once made to keep very fresh. I would probably have just one other choice such as ham.
Cake, sandwiches and some very chocolatey biscuits would be fine - and you will probably have tonnes left.
Might also be fun to have a few different flavoured teas - earl grey, peppermint, etc, - tea bag choices to keep it simple.
You have made me long to get out the best china! Have fun.