But according to good pal Karen Duffy, a.k.a. Duff, not everyone will be shopping at Tiffany's.
At Saturday's EIF Revlon Run/Walk for Women, the model and longtime spokesperson for the brand told PEOPLE she had a much more creative idea.
"I have a tradition where I make needlepoint whoopee cushion covers and bring it to his house," jokes Duff, who's known Clooney, 52, for about 18 years.
"His beautiful home has several of my needlepoints and when you sit on it, it sounds like a tugboat fart."
Still, the former MTV VJ – who briefly dated Clooney – says he shouldn't worry: "I'm sure my husband [John Lambros], who is far more dignified, will find something."
As for her friend's engagement, Duff, 51, says, "It really is a blessing when two people who are so full of dignity and kindness and really live to make the world a better place get together. It's going to be double in their efforts so I'm really happy for them."
But there's one person at her house who had to think about it a bit.
"The one person who is a little bit upset was my son," says Duff. "I was like, 'Uncle George is going to be walking the plank with Amal.' At first he said, 'Good for them.' Then he was like, 'But I really love being his favorite kid.' "
Duff explained that nothing would change that – for the moment. "I told him, 'You'll always be his favorite kid until he has kids of his own.' "
Of Alamuddin, Duff raves: "She's incredible. Truly he is the coolest dude and the greatest friend. They're both hilarious."
She continues, "What I love about George is that he grew up in a family where essentially if you do something good and anybody finds out about it, it doesn't count. So you never hear about what he's doing in Darfur, or what he's doing for displaced people as a U.N. Messenger of Peace. So together with his beautiful bride-to-be, I think they are going to be an amazing force for good."
Reporting by MABEL MARTINEZ