McKidd, who played drug addict Tommy in the 1996 hit movie, has teamed up with fellow Scottish actor Iain Robertson - who he appeared with in Small Faces - and film set chef and restaurateur Guy Cowan to take on Ben Nevis.
The trio are raising money for the Scottish Cot Death Trust (SCDT).
Rab C Nesbitt actor Robertson, 32, is an ambassador for the charity and has already raised more than £14,000.
He said the charity was close to his family's heart after his elder sister Nicola died of cot death.
"The support I have received in fundraising from friends has been incredible. It's all been pulled together last minute, but with Kevin's support and Guy's exquisite picnic to fuel us on our way - I'm sure we'll make it to the top," he said.
Money raised by the trek will go towards publishing a book - Andrew's Rainbow - for young siblings affected by the loss of their brother or sister through cot death.
McKidd, who stars in US medical drama Grey's Anatomy, said: "I know that Iain has personal reasons for supporting such a worthy charity and I'm glad space in my schedule has allowed me to get involved.
"As a parent I can't even begin to imagine what the loss of a child would feel like, I hope people dig deep to help the SCDT continue to offer much-needed support and assistance.
"It's great to be home and taking in the Scottish scenery again, and helping out such a good cause in the process."
Cowan added: "It will be great to team up with Iain and Kevin again, and raise funds for such a deserving charity.
"I have fed both these boys many times through their film careers from Small Faces, Trainspotting and The Debt Collector and, as a result, I have prepared a delicious picnic filled with their favourite goodies to keep them going."