Well, any reason to get out of Irvine is a good reason!
If you haven't booked a room yet, Bewleys is in a decent spot & the rooms are grand. Ask for one on the upper floors facing front, and you'll get a pretty decent view of the city.
Pubs - The Drum & Monkey on St. Vincent Street is an old favourite of mine. Cool decor, big comfy chairs & couches. Just down the road from there - opposite Central Station, is a great place to stock up on cheap drinks before you hit the nightlife. The Goose on Union Street, really cheap drinks, good mixed crowd, never seen any bother there at all. And if it's quiet enough, the grub is ok by pub standards.
Here's a good link to lots of pubs & clubs...
http://www.glasgowguide.co.uk/pubs.html#Bar_Soba
To be honest, most of the "Irish" pubs are either horribly plastic or are just slop-houses. I would'nt be in a rush to get to most of them & I'm not sure I'd be taking my GF into the area where most of them are, on a Friday or Saturday night.
It's a while since I did much clubbing in Glasgow, so I'll simply say that King Tut's used to be THE place, maybe still is, & leave you to browse the links I posted.
If you see anything specific & want to know more, just give me a shout. I'm sure there are others here too, who visit Glasgow often enough & can provide up to date info.