I think producing grains of any sort would require rather too much machinery, unless you already have it. Or perhaps you could just get smallscale hand stuff like rotivator and scythe. I'd love to do the same, but I just don't think it's practical.
I'm thinking this year of sowing more greenstuffs and roots for the other stock. My chooks are free roaming, so live very largely on insects and grasses. We don't mow any of the grasses in their range, so in the autum they help themselves to organic grass seeds !
Where about in the Highlands are you ? I'm in the Islands.