SMD capacitors for a guitar distortion pedal
As @Lundin mentioned, there are other parameters in play. Another is the actual impedance vs. frequency curve. Though for the audio range, there shouldn't be much difference. All of this information should be in the datasheets. I suggest looking up the datasheet for the caps you have as well as the ones from the instructable to make sure there are no big differences.

Another thing to consider is that guitar pedals are objective. Unlike many other questions on this site, you are trying to add distortion, not remove it. Further, you are trying to add just enough distortion to the signal to make it sound "good". That being said, using different components may make it sound better or worse. It's all up to your friend. With SMD capacitors, the leads are much smaller, leading to less parasitic capacitance. Using these components may also shrink the PCB area and mutual inductance. I would imagine it would sound different, but I can't say how much.