Go ahead and ask, the worst that can happen is for the answer to be no ... If that happens, you'll need to decide which is more important ... Keeping the job or disappointing your friends ... If I was a friend, I wouldn't expect you to lose a job over some plans we'd made before you got this job ... That would be selfish! ... With all that being said though, I hope you'll go ahead and ask, and more than that I hope the answer will go in your favor!

Sincerely,
Pfrog!