Amal Alamuddin's conservative Lebanese parents are eager for the couple to make their union legal.
The insider told Us Weekly magazine: "They are old-fashioned when it comes to these things. They expect a short engagement."
A source said: "He'd marry her today if he could, but he wants to give her a dream wedding. It is her first, and he wants it to be his last!"
"George would do whatever makes her happy."
The couple celebrated their engagement with 20 close friends at Café Habana in Malibu, California on May 11.
A source claimed last week: "Amal wants to continue her work, and George is very supportive and proud of her career. He will soon be going to London so they can look for a new home there together."