Tributes will be led by Scottish Lib Dem leader Willie Rennie at St Clement's Church in Dingwall on Monday evening.
Mr Kennedy, a Catholic, died at his home in Fort William on 1 June at the age of 55 after suffering a major haemorrhage as a result of his battle with alcoholism.
"It is only when you read and hear the range and depth of remarks made about Charles in the days after his sad death that you fully understand what he meant to this world," Mr Rennie will tell those gathered.
"From locals to international leaders, so many have expressed their grief and their affection for Charles Kennedy.
"It wasn't just the personal grief, although that was bad enough, but the political grief too. The loss of one of the greats. And the loss of what was yet to come."
The father-of-one had been a Highland MP for 32 years before losing his Ross, Skye and Lochaber seat in May's genera. Her led the Lib Dems for more than six years.
Under Mr Kennedy's leadership, the Lib Dems won a record 62 seats in 2005 but he resigned eight months after the election after revealing he had been receiving treatment for a long-standing drink problem.
The MSP also chose to reflect on some of his personal memories of their time spent together, including an occasion during Mr Kennedy's first public appearance after he stood down as leader of the party in 2006.
"He was mobbed in the streets of Dunfermline, campaigning for me in my by-election. Supporters, journalists and camera crews made progress slow," he said.
"As we passed a shop doorway, a lady of some years called out, 'We love you Charles'.
"Quick as flash, he replied, 'Thanks, but keep it quiet. The party's in enough bother as it is'."
He added: "Charles had a unique combination of political talent and public affection. With that cheeky smile, Highland voice and a few simple words, Charles Kennedy captured the political hearts of the nation."
