What's your timeline for adapting into trail running?

I used to run trails all the time so I never thought I'd be asking this question. Right out my back door I have miles and miles of reasonably technical trails; some loose rock, some scrambling, lots of up and down. There are also some less technical trails right by my work that I can run over lunch. I used to run them frequently and my legs, knees, and ankles seemed bombproof.

Then a few seasons ago I started doing some longer distance tri and began running pretty much everything on the road. I've been missing the trails and I have a race in late July where the run is all uphill trails. Problem is, the last time I went out to run trails I used to run all the time my ITB and left calk went to s**t and my ankles felt a lot less stable. Seems like I've got to build back into it.

What do people recommend? Start conservative, like hikes with the family, and then add in some run-walking/hiking? How long does it usually take for the legs to adapt to semi-technical trails?