Harry and Meghan's attendance is excellent news for Her Majesty, as she will finally get to meet great-granddaughter Lilibet Diana, who will be turning one in June, for the first time, as well as catch up with three-year-old great-grandson Archie. It will also be the first time Prince Charles will meet his granddaughter, who he previously said he was "incredibly sad" not to have met yet.
We don’t yet know what the extent of Harry and Meghan's participation in the celebration will involve, and whether they will be joining Her Majesty on the balcony after the jubilee pageant on Sunday, June 5th. The Queen's appearance on the balcony – as well as whether a balcony appearance will happen at all – is still undecided, and it's likely that it will be decided at the last minute, depending on the 96-year-old monarch's health.
The Queen has imposed an 'only working royals' rule on the balcony at the Trooping the Color event on June 2nd, which will mark the start of the jubilee celebrations, so if a second balcony appearance will occur, it's likely that the same rules will apply. According to The Guardian, a Buckingham Palace source said: "After careful consideration, The Queen has decided this year’s traditional Trooping the Color balcony appearance on Thursday June 2nd will be limited to Her Majesty and those members of the royal family who are currently undertaking official public duties on behalf of The Queen."
This therefore doesn’t include Harry and Meghan, or Prince Andrew, who has been stripped of his military affiliations and royal patronages. But we can expect to see Prince Charles and Camilla, Duchess of Cornwall, the Duke and Duchess of Cambridge, the Earl and Countess of Wessex, the Princess Royal, the Duke and Duchess of Gloucester, the Duke of Kent and Princess Alexandra all up there with Her Majesty. Harry and Meghan will, however, be included in other jubilee events such as the service of thanksgiving at St Paul’s Cathedral.