Well the Huguenot Park are is one idea. It connect to Robious fitness club[new name Midlothian Athletic club or something similar].Tuesday nights there is a RRRC sponsored run there and also at the other end of Huguenot going into the city just before the bridge, go down to the Pony Pasture and run loops in there. The trails are very flat, but do have variety.
I just started a Trailing Running Group now. So, if you'll send me your email address, I'll invite you to join. I'm guessing that's how it works. I'm not sure if anyone could just join it, without me having to do it this way. I'm not big on the whole Facebook thing, and I know this very similar to it.