The former Liberal Democrat leader said that many people did not want "shrill exaggeration" in the independence debate.
He also accused the SNP of centralising power in Scotland in a way that would have "shocked" Margaret Thatcher.
The Ross, Skye and Lochaber MP said that there was a need for a "distinct tone of voice" for the campaign in the Highlands.
He told campaigners in Inverness: "Ours is not a mirror image of the essentially Labour-SNP battle taking place across the Central Belt.
"While all the same essential questions being posed of the Yes campaign apply, both the political geography and campaigning history across our unique area of Scotland requires even more emphasis on the constructive and the positive. Voters here do not want shrill exaggeration, they want sensible engagement."
He also said that there was a "pressing need" for the pro-Union Better Together campaign to set out soon what the benefits of a No vote would be for the Highlands and Islands.
He said voters should be given an offer of more devolution, within and across Scotland, and "nowhere more so than here".
He attacked the SNP Government for what he said was a power grab, of the kind that even the party's arch nemesis, former Tory Prime Minister Mrs Thatcher, would not have attempted.
"This SNP Government has centralised within Scotland to an extraordinary extent - and to the specific detriment of the Highlands & Islands," he said.
"We are seeing it over fire and police services; we have previously experienced it over the Crofting Commission and Highlands & Islands Enterprise.
"Even Mrs Thatcher, at the peak of her powers, would have baulked at such political audacity," he added.
Mr Kennedy said that a more positive approach would "resonate with voters from across the political spectrum and across the Highlands & Islands. I recommend them to our campaigners".
Better Together has come under fire from opponents who accuse the campaign of being too negative in its outlook.
Rob Gibson, the SNP MSP for Caithness, Sutherland and Ross, said that part of that positive message was that Highland politicians would have more influence as part of an independent Scotland than they currently do as part of the United Kingdom.
"(Independence) will give the Highlands & Islands and the key industries we rely on to build livelihoods and prosperity here far more influence in an independent Scotland than can ever be the case at Westminster," he said.