Shun Cheung , Aug 05, 2008; 01:07 p.m.
I would try to use existing light as much as possible. A flash will kill the mood for the most part. If your daughter is also in the picture and there isn't enough light on her, maybe add a bit of fill flash. Your wide anlge and the standard 30mm lenses will probably be the most useful ones.
Are there going to be a lot of people? If so, I wonder whether the environment will allow you to use a tripod because that will really slow things down. Plus if the balloons will be moving in the wind, you might not be able to use a very slow shutter speed. Unfortunately, for some of these issues you have to be there to decide what is best approach for the situation.