If I were to want to be able to use a pre-prepared synth part off of my laptop, how do I keep it in time? There's an option to tap the tempo on the program, but that'd inhibit my ability to play other instruments. Is it possible to use a pedal to tap the tempo instead, so the pre-prepared part will stay in time with the other musicians?
You're looking at it the wrong way round, you want to be putting your drummer on a metronome, so you're always in time with the synth.
Normally the way to incorporate prerecorded parts into live performances is having everyone on click tracks. That's probably not an option for you. Is this a midi file you're playing through a VST?

It depends on how long your prerecorded part is, but your best bet is probably just practicing playing in time without a click track.