"I will wear Prince Rainier's uniform, Spatzi will be dressed as Grace Kelly and the master of ceremonies will be an Elvis impersonator," the 81-year-old Viennese society figure told the Austrian Press Agency on Thursday.
Although the spectacle will take place at the newly opened Wedding Chapel in Casino Velden, Lugner still has no plans to marry his sweetheart.
"We'll leave out the marriage registrar," stressed the billionaire, even though things with his 24-year-old Spatzi are reportedly going well.
"Apart from the big age difference everything fits. Of course I argued less when I was alone, but a man needs a partner," opined Lugner.
The pair will arrive at the event in typically impressive fashion.
Spatzi will be brought to the casino by her father in a motorboat, while Lugner will drive up in a white Thunderbird car with red leather seats.
"I actually want to celebrate this engagement with a small group," said Lugner.
The billionaire builder's recent weight gain has attracted great media interest, as has the couple's May-December romance.
"You would not believe how much the German media write. And not just provincial newspapers, but the Frankfurter Allgemeine, Die Bild and Die Süddeutsche Zeitung. I don't want to imagine what will happen if I get married again," Lugner said.