I'm 28 and up until I was 23/24, never bothered with the Flu Jab, the usual "It won't happen to me, I'll be fine if I do get it" thoughts of a young bloke who thinks they're partly invincible I guess. I ended up catching the flu in the winter of 2007, I can't really remember much about it, was slipping in and out of consciousness a lot, was in hospital for around 4 weeks, family thought I was on the way out, thankfully I fought it off and luckily I'm here to tell the tale!
That was obviously a wake up call, I had a wee boy who was only 1 year old at the time, and I think I matured overnight! I've had the flu jab every year since then as soon as it's been available with no ill effects, it's pretty much a painless injection, I only had a sore arm once and that was down to the nurse hitting a muscle I think, all other times it's been fine and I've felt great the whole winter.
My advice, get it done, chances are you won't catch flu, but you're better safe than sorry, and you've got a responsability to the vulnerable people you'll be working with, so I don't really think there's a decision to be made.
Hope you make the right choice and you have a healthy winter!