The couple has previously undertaken a 100 mile bike ride in aid Martin House Hospice, and are now hoping to raise money and awareness for Get Fit 4 Mental Wellness, based in Sowerby Bridge.
Tom Jones and his partner Corrinna Matthews will be climbing Snowden, Tryfan, Helvellyn, the old man of Coniston fell and Scafell Pike over three days, starting on July 29, and will be joined by some of their friends along the way.
"We are all nervous about the challenge," said Tom, "as we are doing the longest hardest routes possible up each mountain."
Tom, 37, and Corrinna, 35, have been together for nine months and got engaged four weeks ago.
"Myself and Corrinna have attended the charity over the last year and taken part in the revolutionary eight week programme that helps you deal with your mental health issues.
"Since doing the programme myself, Corrinna and our friend Joanne have all become vital members of the voluntary team here at the charity, giving back as a way of saying thanks for what they have done for us.
"We now support people who attend the charity and run walks for the new people to try.
"Every day we see people who are struggling with mental health issues - grief, loneliness or just needing that extra bit of support.
"So we are doing the walk to raise founds for the programmes and to raise awareness of the charity with an aim to make the service more available. We would like it to become a seven day service."