Hope your DD is doing well!
Sorry 'bout the correction for the spelling...it's a pet peeve of mine, but also, you'll sound way more experienced at tri if you spell it right!
Frontier is reasonable with bikes, I've used them before. If you're good with taking it apart and putting it back together, you should be good to go. But if you do decide to rent (or consider it), most places should be able to rent you most any kind of bike. I rented a hybrid when I travelled for my 2nd tri (hee! same as you!) because that's what I was riding at home at the time. You could even rent a mt. bike. And just FYI, for any tri, not just Danskin, they don't care if you own, rent, or borrow the bike. It just has to be in good working order (esp brakes) and have the handle bar ends plugged.
One thing if you bring your own bike or even just your own biking accessories...if you use CO2 cartridges to air up your tires (some use them for racing, in case they flat, instead of carrying a frame pump), you cannot bring those on the plane at all (not checked nor carryon).
I'm psyched for you...read some of your pre-trip stuff! Welcome to the triathlete family!

And...Bay Lake isn't really that bad to swim in...but I've only swum in it in May for the 1/2 Ironman series. I hear it gets hot (and prone to those amoebas) in September. That could be why they moved the race. Or just the hassle of the race crews dealing with Disney. The Disney sports team doesn't put on the race...Trek, or Danskin, or Ironman comes in and has to go by what Disney will allow on their property. It's all good, though.
yay for you! and good luck!! PM me if you come up with any other questions. I'm going into my 12th year doing tri and I love it!