A Sydney 50th Birthday
For the occasion when the budget is no constraint and the night should be remembered.

Sydney is the right city to mark a fiftieth, particularly for the harbour-loving guest. The combination below assumes a budget around AU$45,000-$60,000 for fifteen guests, an evening event running from late afternoon to past midnight, and a host willing to pre-book three months out.
The trip we would do: a late-afternoon-to-eleven charter on Sydney's largest exclusive-hire vessel, a private chef on board for a four-course harbour-side dinner, a magnum hour at the Bridge anchorage as the city lights come on, return to dock by eleven, helicopter transfers for the older guests, and a small after-party at the Bennelong Bar.
The picks

Charter, 5pm to 11pm
Tango
Australia's largest exclusive-hire superyacht. Forty-nine-guest day cap leaves room for fifteen plus a chef, a photographer, and a musician. The beach-club deck on the lower stern is where dessert happens with the lights on the Opera House. AU$4,500/hour, around AU$27k for the six-hour booking.

Helicopter transfer for guests
Sydney HeliCharter
For older guests, a two-passenger executive helicopter shuttle from Mascot Heliport to the Crown Sydney heliport on Barangaroo. The timing-and-evening-dress logistics work better than a car. Allow AU$2k for two guests round trip.

After-party, 11:30pm onwards
Bennelong
The Bennelong Bar (separate from the dining room) is the right Sydney late-night close. Reserve the lounge area; bar tab roughly AU$1.5-2k for fifteen at three rounds.
The four bookings (yacht, chef, helicopter, after-party) need to lock three months out for a Saturday night in spring or summer. The helicopter transfer is bookable two weeks out. Total indicative spend AU$45-55k, before flowers and photography.
The variant we would propose for a smaller party (six to ten guests, half the budget): a smaller charter from Lifestyle Charters (Sirenuse), the same chef, no helicopter, dinner finishing at Margaret in Double Bay rather than the Bennelong Bar. We can publish that variant on request.