Tall order.

Part of why I say that is there are literally hundreds of options available.
Thousands if you include every aspect- keyboards, computers, software, synth modules.
If it was me I'd get a rackmount sampler. A nice Akai or Emu, something with a relatively big LCD screen. You would use it to record, edit, and play back the clips that you want to play back. For the synth sounds, you can buy discs of samples of synths specifically for the Akai/Emu/whatever libraries. I'd choose the hardware sampler over a software program for a laptop just because I have personally had laptop glitches and freezes on stage too many times.
That said, there is so much amazing software out there, that can do all the synth, sampling, editing, and everything else you'd want, that it's easy to see why people go that route. It's cheaper and does more than buying separate hardware devices. But again,
for me, the laptop idea just didn't work out- partly because I underestimated the huge amount of processing power required to do the job.