The keys to being considered a cool parent at your Daughter's 18th birthday party, and therefore be in the running for the coveted Parents Of The Year award, are...
Agree to have it at your own home, against your better judgement, despite all the news stories of gatecrashers and neighbours calling the police. Just don't admit that due to fortunate circumstances, the houses all around you will be empty on the night anyway.
Hire a jukebox which allows the birthday girl to choose in advance the music programmed into it, so that when the kids are too hammered to select songs and let it play on random shuffle, there is no chance they'll be serenaded by Engelbert Humperdinck or worse, Justin Bieber.
Make an enormous birthday cake of the birthday girl's choosing, with whatever design she wants. And by 'make', of course I mean 'buy' from Wicked Sweets.
Spend several days scouring all the cheap shops, buying up every packet of purple cups, plates and forks you can find, just because it's her favourite colour. Then spend several days after the party scouring the back yard, picking up purple cups, plates and forks.
Provide a sturdy playing surface (ping pong table will suffice), brightly coloured ping pong balls, and enough of the aforementioned purple cups for a rousing game of Beer Pong. And by 'rousing', I mean ohmyfuckinggod.
Serve colourful Vodka Jelly Shots to cheers, wows, OMGs and emphatic "You are fuckin' awesome" declarations. Just don't let on that the amount of vodka in them is nowhere near as much as the kids think.
Don't panic or get angry when you hear the words "Someone just vomited in a pot plant". Send the Husband out to deal with it.
Don't panic or get angry when the allotted toilet area (in the laundry) starts to take on the smell of a decomposing body. Send the Husband in to deal with it.
Accept with grace the fact that your nice bathroom will have to be used while the offending body fluids are dealt with and the whole laundry is disinfected and aired. Also accept, though with less grace, that an indescribable smell will remain in that laundry for a couple of days.
Shut yourself away inside as much as possible, and only venture out amongst the wild animals when absolutely necessary. Exceptions apply when a song you want to dance to comes on, especially if you've had a few wines during your seclusion and just can't help yourself.
When making an unavoidable visit to the party zone, keep your eyes averted from the amorous couple on the chair. And the couple on the lazy lounger. And the couple on the lawn. Do, however, quietly and stealthily check the girl's hair for bits of grass before her father picks her up.
Try to act normally when someone gives the Daughter a meat cleaver as a gift. Don't ask.
Do a second run for pizza when the first lot disappears in five minutes flat. Don't let on it's because you wanted to keep some aside for lunch the next day.
At no point should you stop to add up the financial cost of the party. This is not really to be cool, but for your own sanity.
Laugh at everything. This is where the 'few wines during your seclusion' comes in handy.
Remember how it felt to be 18.