She's visiting the same exact day I promised a close friend that I'll go to her party full of a dozen hot babes. My 2 buddies and I are the only guys so far.  

Book her , Bang her then party Hearty !!!! Always time for a 12 Hot Babe Party !!!!!  
Or you can just take her to the party and make it a Mind Boggling Experience !!!!
Just my 1 1/2 cents....Good Luck !!!

Would depend for me on whether the partygoers are bangable or not.  Hot is one thing, potentially willing is another.  Sometimes groups like that can be hard to split up and do any more than get a phone number and possible interest.

you are getting laid at the party, I would go to the party and then bail out a little early to see the hooker.  

How likely are you to pull ass out of the party?  

for rounds 2+.  Might be called the best of both worlds.

a hand in the bush is better than a bird in the hand...

So true..but he has'nt a hand the bush.
I would go for the sure thing..booking...then...party.

One was about an 8 in appearance and another was about 9 in looks.  

to do it within an hour. I like 5-6 hrs of rest to recharge. I mean I would be able to do it within hour but just wouldn't be as much fun....