Our drummer suggested that we play this song at our school's band night this summer, we were planning on playing 2 originals, Iron Man and this, (we get a 15 min set

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Ive got a couple of questions I want to ask.
I was wondering, since this song doesn't have 2 guitar parts(At least I don't think it does) If we should just make one up and have a guitar part take the place of the keyboard.
Or, I could just play the keyboard part(I play rhythm guitar normally) on a keyboard instead.
I'm worried about getting the synthy sound, since between us we have 1 synth pedal(my bass pedal) and the other guitarist's amp has a few effects on(phaser, flange, etc...)
I think It might be far easier if I did the keyboard part rather than trying to emulate the sound on guitar.
Anyway, anyone played this before? what did you do in terms of instrumentation? Any other tips?