The 'Angels' singer has sent out invitations to around 100 family members and close friends - including Simon Cowell, Adele, Sir Elton John and Petra Ecclestone - to invite them to celebrate at the couple's home in Malibu on May 17 and is planning to pull out all the stops to make it a night to remember.
A source told The Sun newspaper: ''Robbie's been really excited to plan the party, although it's not a surprise because he knows Ayda would freak out if there was a big party and she hadn't picked her own outfit and pulled out all the stops to look and feel her best.
''There's a bit of a buzz of excitement about the event as Rob and Ayda pride themselves on throwing a good party and never disappoint.
''Plus it's at their place by the beach, so it's a beautiful setting and will be catered at a really high standard, with vegans and vegetarians particularly well catered for.''
The party will also mark 20 years since 45-year-old Robbie - who has children Teddy, six, Charlie, four, and seven-month-old Coco with Ayda - got sober.
And the 'South of the Border' hitmaker previously admitted it's ''miraculous'' that he's been able to avoid booze for so long.
He said: ''I'm an alcoholic. I like booze. That's the one that stayed with me, going to meetings, going to rehab, getting this information.
''It's miraculous because I'm drawn to getting f***ed up.''
Robbie recently drew comparisons to his current life and former wild lifestyle and admitted things are ''much better'' now.
He said: ''Back in the 90s, it used to be strippers and cocaine and now it's hummus and celery and my life is much better for that. I used to live on rock star hours, which was go to bed at three or four o'clock in the morning, and wake up in the afternoon. You quickly realise when you have a child you are not an insomniac but a bit lazy and prone to exaggeration.''
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