I think I'd vote for #1 if I'd go live. That is:
LAPTOP (from where you get your sound banks) --> INTERFACE (as in a MIDI keyboard to trigger the sounds) --> MIXER (actually you'd have to have that USB input/output interface to hook to the mixer) --> P.A.
I've seen a friend from Urbanation do that setup, if I'm not mistaken. I personally think that the mixer has an advantage kasi you could hook up headphones instead of relying on monitors. Atsaka hindi kasi lahat ng bars may monitors, as per my experience, so bringing a headphone set to monitor might come in handy.