Mom2, Happy Birthday to your dd
My guess is that five-year-olds are not fond of tea, but like the idea of dressing up and tea cups, to be grown up like mom. IMO, clotted cream, scones, mascarpone, watercress sandwiches etc., appeals to adults - not kids. Guessing kids would be happy with cake, candy, chocolate, hot dogs and ice cream.
Some ideas that might be more kid friendly:
Maybe lemonade in place of tea in their teacups.
Chocolate chip cookies and ice cream
Pigs in a blanket (instead of scones)
Chocolate dipped strawberries (or leave out the chocolate) or a pretty fruit plate
Fruit skewers (i.e. melon, grapes, cheese, etc.) & a yogurt dipping sauce
A Tea Party theme Birthday cake
Music that appeals to kids (not classical)
Tea sandwiches like peanut butter/jelly, cream cheese. bananas - why not some s'mores
Dress up the plates with little doilies
Thumbprint cookies (jam, almonds etc.)
Maybe a fondue with fruits for dipping
I wouldn't go overboard with the sweets. Maybe have an Alice in Wonderland/Mad Hatter Tea Party theme. Rent a video of Alice in Wonderland.
Just a few ideas to get the ball rolling. Hope the party is a big success.