The 'Lift Me Up' hitmaker is to tie the knot with Infiniti Red Bull Racing Formula 1 boss Christian Horner in May and all her former bandmates - Mel B, Mel C, Victoria Beckham and Emma Bunton - have promised to be there for her big day.
A source told The Sun newspaper: ''Geri is desperate for all the girls to be there. Some of their schedules are tighter than others but Geri's happy it appears there'll be a full-on reunion at her ceremony.''
Mel B is said to have the most trouble committing but is still expected to be there in what will be the group's first reunion since the premiere of their musical 'Viva Forever' in London in December 2012.
While the Spice Girls will be at the wedding, which is expected to take place at Syon Park House in west London, it was previously claimed 41-year-old Christian's parents won't be there.
His father Gary and mother Sara are said to have refused to attend because they are furious that he left his partner of 14 years, Beverley Allen, just months after she had given birth to their first child, daughter, Olivia.
An insider said: ''You can say that his parents are absolutely devastated. We won't be going to the wedding. There is a lot more to this story than people know about - to do with his ex-partner.''
A friend added: ''Over the years Christian has been very close to his parents - particularly to his dad who shares his love of motor racing - but recent events have thrown everything into doubt. His mum is particularly upset.
''It's a real shame and everyone involved is upset. Weddings are expected to bring families closer together, but this engagement has driven a wedge between people.''
The couple, who have been friends since 2009, started dating in March 2014, and rumours have been circulating for some time that they are set to tie the knot.
Geri, 42, has an eight-year-old daughter, Bluebell, from a previous relationship.
'Smalls Change (Meditations Upon Ageing)' arrives in April.
The two awards have made for a great 72nd birthday present for the country music icon.