Julie-Ann Coll and her mother Catherine Cooke, both from Derry, received separate invites around 90 minutes apart and told of their shock and delight.
Mrs Cooke, 53, said she could not believe it when the postman arrived with the news, not long after coming off the phone to Julie-Ann who had already learned of her own invite.
Mrs Cooke, who was chosen for her work with Foyle Women’s Information Network, which provides opportunities for women’s groups to meet from across the county and discuss various issues, said she was “very excited and very honoured”.
Her husband, who will be on a stag do in Krakow that weekend, was “devastated” that he cannot attend, she said, adding that she will take another daughter Stephanie to the big day instead.
Mrs Coll, 35, was nominated to attend for her work with child bereavement support group Life After Loss, having lost her son Mark in 2004 at 22 weeks old.
She will be accompanied by her mother-in-law Marcia Coll who she joked is “probably online shopping as we speak”.
“I’m just over the moon but I can’t picture myself being there to be honest. I’m just so excited,” Julie-Ann Coll said.
Ex-Royal Irish Regiment soldier Phillip Gillespie said it is “a wee bit surreal” to think he will be there next month with his girlfriend Kirsty Crawford.
“It’s a massive privilege, it will be a huge spectacle,” he added.
The 30-year-old, who lost his right leg in Afghanistan in 2011, is also eagerly awaiting news as to whether he has made the rowing and archery teams for the next Invictus Games – a brainchild of Harry.
Mr Gillespie, who is involved with ABF The Soldiers’ Charity, said he was looking forward to a busy few months with the Invictus trial results, the wedding and then a royal garden party following his BEM award last year.
He said he had not told many people yet but expected his friends’ reaction to be muted, compared to the feedback his girlfriend was getting.
“I think Kirsty has got more of a reaction, I think it (a wedding) is more of a girl thing,” he laughed.