We mostly have 'family birthdays' here. Meaning we do something special as a family, usually with Grandma along, sometimes with other extended family or those lovely adult friends who are as-good-as-family. Because really, we're pretty introverted here and have never build up the expectation that one must throw a big social event on one's birthday. My older kids both tried out the social event thing a couple of times, and we did some pretty neat stuff, but mostly they've got more enjoyment from creative family-oriented things at home and away from home.
Fiona wanted to go to the Domes. Dinner, with some time in the sauna and the hot tub under the stars, and then a quiet family sleep-over in the large dome-shaped cottage at Villa Dome Quixote. Of course Grandma must come to dinner and for a soak, but she also wanted to invite one of her very special favourite adult friends.
And so she made up a tiny invitation, and together we folded a matching envelope. And then, to seal the envelope we decided to use sealing wax. We have a couple of brass seals and a few sticks of traditional sealing wax. They're kept in a wooden 'writing box' which I stocked a few years ago with pens, paper, envelopes and postal accoutrements in order to inspire the kids to write letters. I confess we entirely forget to use the post for correspondence most of the time (in this family even the youngest members have their own e-mail accounts) but it is so quaintly fun to dribble wax and affix a beautiful-even-in-its-globby-asymmetry seal to an envelope.
These folks sell lovely stuff. Wooden handles or Murano glass on brass monogram seals, pens and ink, deep red wax candles. Just promise me you'll stay away from the hot-melt glue-gun "wax" and the peel 'n stick seals they also offer.