I don't think you should decide you need a wider tire based on any internet reading. Personally, I've gotten a little tired over the years of reading stuff about the advantages of fat tires. I wouldn't go super narrow, but 25 mm shouldn't be a big problem, really. Just make sure it's a true 25 and not something smaller. I don't know about your specific bike, but one thing I do know is that if you can fit wider tires on it, you should still ensure you have a bit of clearance, because you may need it on packed trails. The best way of knowing if it works would be to just break down and buy a cheap tire in the size you want.
If it was me, and if I really was going to ride on trails that my road bike couldn't handle with its normal road bike tires, I might consider just getting another, cheap bike for that kind of riding.