Anyone have any experience? I'm facing a challenge and could do with a few pointers. Here's the problem:

To begin, some background.

I've been pulled into engineering the sound for a small gig this Saturday. A medium/large size pub, 3 bands (drums, a few guitars, bass and vocal), an insane metalhead's birthday party and our good friend andrewcc. Mix in a lack of experience with this kind of thing, very limited budget and equipment and lots of beer and wee have a recipie for disaster.

What wee have:

2 small condenser mics.
A few assorted dynamic mics.
An 800w PA system with a powered mixer (mixer with power amp built-in)
Various leads.
1 or 2 mic stands.
Me + Laptop.
Beer.

What I'd like to do is re-enforce the bands playing but also record one of the bands playing. My plan goes as follows:

Not bother micing up the drumkit. The room is small enough. Choose the 3 best guitar and bass amps out of all the amps that the 3 bands have brought. Mic these amps so that the mics don't have to be moved to other amps between bands playing. Run all of these mics into the powered PA mixer and output to speakers. Meanwhile, at the back of the room, set up the pair of condensers and run these straight into the laptop. Take an output from the powered PA mixer and send into the laptop also. Record a blend of these signals. Also have an output from the laptop to the PA for playing background music before and after the bands play.

Anyone see any problems or possible difficulties based on that setup? Any recommended changes?