Dear R.,
I responded to a Princess party in this way. Perhaps you could adjust it to include tiny finger(cucumber, cream cheese) sandwiches, mini muffins, tiny cheese and crackers or mini cookies since tea parties feature mini foods, not meals. Include paying a sincere compliment to each guest, introducing each guest to others and thanking them for their joining in pleasant company.
Of course every princess has been enrolled in finishing school so they know all about manners and walking nicely keeping a crown on their head, and carrying a cup of tea without spilling.
First, start the game for the duration of the party with the announcement that each time a guest says Please or Thank You, they get a little bracelet--those little neon rubber things--cheapo.
Secondly, Princesses in training should be able to walk across the ballroom or lawn (15 feet) without spilling their tea-use gingerale, or something clear,(no stains) but Certainly not water--too common) which is filled to the brim of their plastic tea cup. They will be on tippy toes (as per high heels) of course. You may politely drink what is left.
Thirdly,
Princesses should come quickly when their Queen Mum calls them (same 15ft) without losing the tiara on their head.
Of course princess in training need lots of reminding to use manners to make sure they receive all the bracelets at every opportunity.
If a participant should (Heaven forbid) bump into another,or spill their drink on someone, if she says "uh,oh, whoa"--1 bracelet. "I'm sorry" gets 2 bracelets, and of course, "excuse me" earns 3 bracelets.
Should a grande faux pas occur, the princess who says,
"my bad" shall forfeit all bracelets. ;)
AND in the event that she immediately corrects herself and says "I'm sorry" or such, her bracelets are immediately restored to her lovely arm.
The pleasure is all mine, C. ;)
ps. Should a prince attend, he shall require a necktie borrowed from his father, or supplied by the hostess.
Princes are often peculiar about bracelets and may trade them for candy/toys as they prefer at party's end.
pps. I'd be ever so pleased to know that your daughter and her guests enjoyed themselves. Take pics--they will make a nice surprise in a high school annual at graduation or future wedding shower. =)