The 29-year-old journalist was shot dead by the New IRA terror gang last Thursday while observing rioting in Derry.
The President of Ireland Michael D Higgins, Taoiseach Leo Varadkar and leaders of political parties in the North of Ireland’s will also attend.
Ms McKee’s family paid tribute to their “gentle, innocent soul” whose “desire to bring people together made her totally apolitical”.
They described her as having a “warm and innocent heart, the greatest listener and someone who had time for everyone”.
She was a “smart, strong-minded woman who believed passionately in inclusivity, justice and truth”.
They said they were thankful for the huge outpouring of sympathy in recent days, and that she should be remembered as “someone who spoke to and made friends with anybody and everybody, no matter what their background”.
That will be one of the themes of the funeral service, with Protestant and Catholic clergy taking part and politicians from across the political divide in attendance.
The journalist and campaigner for LGBT rights is survived by her mother, two brothers and three sisters.
Her funeral is to be held at St Anne’s Cathedral in Belfast, and the service will be led jointly by the Anglican dean of Belfast, the Very Reverend Stephen Forde, and Fr Martin Magill at 1 pm.
Ms McKee’s partner, Sara Canning, said the service would be a “celebration of her life”.
“If people would like to wear Hufflepuff, Harry Potter or Marvel related T-shirts I know she would love it,” Ms Canning said.Secretary of State Karen Bradley will be among the dignitaries attending the funeral.
Fellow members of the National Union of Journalists (NUJ) are to form a guard of honour at the cathedral.
The union described Ms McKee as “one of the most promising journalists” in the North of Ireland.
There will be a gathering at Guildhall Square in Derry at 13:00 BST for those who cannot attend her funeral.