This is gonna be a looooooong post!
A few years ago, we threw a "High Tea" birthday party; everyone wore pretty dresses and over-the-top jewellery, etc. Because she's only 5, it's quite likely that most of the little girls won't want to drink tea so as well as sweet fruity teas, we had pink & regular lemonade, pretty coloured fruit juices in big jugs, and we drank out of milkshake glasses with paper straws
For food, little baby cupcakes with pastel icing; little sandwiches without crusts cut into triangles; maybe slices?; fruit (although a lot of the time it gets left uneaten. Sometimes if you make fruit skewers the kids are more likely to eat them) like strawberries, kiwi fruits, watermelon slices, etc. Something really fun is if you can get a little chocolate fountain - about $12 from K-mart - and dip strawberries and marshmallows in.
For decorations, you want lots of floral, lacy, girly stuff. Hit up the thrift shops and go looking. It doesn't all have to match! Bunting flags are always pretty, and depending on what time you're thinking of having the party maybe some fairylights
Maybe for the goodie-bags, you could make little baskets with each kid's name on it and use them as placecards? I think you're definitely right about the three-tiered cake stands, they're very feminine and you can usually find some at thrift stores and while you're there, maybe you can look for some odd teacups and saucers to have around the place. Streamers in pretty colours, lots of glitter and lace
I think that the beanbag game sounds really good, but maybe use a laundry basket instead of a bucket so that they're more likely to get it in. I like the hat idea too! If you have some old beading stuff lying around, you could let them make jewellery. And if you have dress-ups, fashion runways are usually a hit! I also like the previous repliers idea about getting the older kids to decorate cookies to go in the goodie-bags, that should keep them occupied for a little while. By 12-ish they can usually entertain themselves, but maybe have some boardgames out to give them something to do. And don't forget to use them as slaves!
Anyway, hope I said at least a couple of useful things. Looking forward to photos!