I would go straight to clipless. If you're used to them already, it shouldn't be too tough. You might fall a couple times, but you'll be fine. Just be sure to start on a beginner trail!

The only difference between road and off road with clipless is the amount of time to unclip. Normally on the road you have some time to unclip, you can think about it, for off road though you have more moments where it's just instinct. If you're used to your pedals though and it's intuitive for you to twist your ankle to get out, I don't think you'll have any problems.