What is the lesser evil, degassing too early or too late?
In my experience (and I'm only an amateur baker), you could leave this until you get back and knock it back then.  If you leave it really long (e.g. 24 hours), you might find it just doesn't have enough life left in it to rise again properly after, but an extra hour or so will probably improve it - I've always found that recipes err on the side of speed.  

For a 2 hour prove time, I'd keep it slightly cool but not fridge-cool.  Since you're using a very wet dough, you will find it gets a little stickier the longer you leave it, so might need slightly more flour when shaping.

Having said that, I've recently been experimenting with really long rise times (12-24 hours, for ciabatta) - I just haven't found a happy medium yet that suits me.