Sorry, I have a 18-55 and a 55-200. I will have them both with me,but feel I will be using the 18-55 more. The atmosphere is an outdoor nature preserve, but participants will be able to hold and get very close to the birds (I've never been, so I can't say how close exactly, but I've seen pictures from past events in which its sort of like a camp fire setting).
Aperture mode is what I've shot in and have the flash pop up on it's own accord.
Take the 55-200mm lens as Deezey suggested. Less distortion and has reach just in case you needed it.
As to the shots themselves, it will depend on how close you are and what bird it is and if its small or large.
First, keep your lens somewhere off of either end of the extreme zoom range. For example, shoot close shots at say 60mm length and telephoto shots at the 180mm length. Some lenses don't like either extreme end of their zoom range.
Second, if you are close to the bird and it is relatively still you can use the AF-S mode for AF Single servo. This will allow you to get locked focus directly on the eyes of the bird which is what you want. If you are shooting a bird that is moving a lot, or even flying around, set the AF mode to AF-C for continuous focus servo.
I would plan on using Aperture Priority Mode, set aperture to f/8 to keep enough depth of field to get all of the bird in focus. Shutter Priority is fine to stop motion blur but you will need to keep your depth of field in control or you will come out with a lot of out of focus bird shots.
If you do use a wider aperture, say f/4.5 or f/5.6, you will need to be very diligent that your focus is on the eyes and that the eyes are perfectly focused. If not, you will have a bird with blurry eyes and sharp, in focus, neck feathers or beak area.
If it were me I would use Auto ISO and set the ISO not to go higher than ISO 800 so you can keep the grain and noise levels down. While in that menu set the minimum shutter speed to not drop below 1/1000th sec. If you have good daylight this will work.If its cloudy or dark day you will not get away with this setting.
Make sure the sun is coming from behind you and lights the birds body without a ton of shadows or without a silhouette.
I suggest to shoot RAW/NEF format if you have the software to edit and work with RAW files. If not, shoot JPEG High, set sharpening levels to +7, and set color to Vivid.
Also, read this entire thread I started. You will see my progress from horrible bird shots to what I consider are fantastic shots because of the help I got here on this forum.
http://nikonites.com/wild-life/17882-my-bird-shots-just-horrible-i-need-some-help.html#axzz2ydlnmVrS