The commoners who will receive the coveted invitations are likely to come from the charities that the prince and his bride are close to, sources tell PEOPLE, while denying a report in The Sun on Wednesday of a Willy Wonka-style lottery.
It's not clear exactly who will be invited, but palace staff are expected to use the 1997 funeral of William's mother Princess Diana, which was attended by many charity workers, as a model.
That means campaigners for causes like homelessness, children's welfare and cancer awareness – from groups like Centrepoint and Starlight – could be invited to William and Kate's nuptials. "They are areas that the couple would like us to explore, but it is too early to be specific," a palace source tells PEOPLE.
The involvement of people outside their immediate family and friends in the Westminster Abbey service marks a desire by the couple to inspire a national day of celebration. There is even talk of a pop concert and big screens being erected for people to watch the event in open spaces.
William's private secretary said Tuesday, "Prince William and Catherine have made it very clear that they wish everybody to be able to enjoy the day with them."
In other news, Kate will be keeping her dress secret from her fiancé (and the rest of the world) until the big day, but there is speculation that her choice of designer will be announced soon.