Hi Abee and Charlotte, The Warwick Cancer Foundation was specifically set up to support people diagnosed with cancer between the ages of 25-40 (an often overlooked demographic, as you can both appreciate)They're a national organisation, based in Melbourne. They have 'members catch-ups' a few time a year, and a peer support program which 'buddies' people in the same demographic and the same cancer (if available). They can also provide practical and financial assistance.
My husband has been a member since he was diagnosed with lymphoma 3 years ago, and they have been really helpful for both of us (although, Charlotte, you may need to know they definitely concentrate more on people with cancer than their supporters/carers).
Having said all that, I think your idea is great! I only mentioned TWCF because it might save you having to do so much ground work. Please keep me posted. Emily