I agree that it will probably be sufficient, but it's difficult to say for sure. If you're inside of a housing or near other parts or something that will also decrease efficacy, so even if open air with the fan on will be sufficient, that's no guarantee for every environment. It's also worth noting that the max temp spec on the LEDs may not be high either, and even if the heatsink can get rid of the heat, if the temperature it equalizes at is still too high for a lower-spec LED die, you'll be out of luck soon enough.
The way to be sure, as with many of these cheap things off ebay or what have you, is to try it. The specs, when available, aren't even necessarily accurate in a lot of cases, so even if you've got full specs for everything.... maybe your fan RPM is 20% low, or maybe your LED actually only uses 6W. A highly efficient 10W LED will also produce less heat than a less efficient one (more of those 10W will be turned into light), so there can be some variance in heating requirements there, too. There's even a chance that under-driving the LED only a little bit makes a comfortable margin with this fan whereas it's at its limits or longevity of the LED is considerably less.
If you're cooling a bunch of lights though, and they don't have to be individually mounted, maybe consider something like aluminum channel strips. Not as much surface area as a standard heatsink, but it's easy to just force air along it and you can mount several LEDs in a row with only a few mounting holes.