After reading the post again, I am understanding that you will take the phone no matter what. The question is if you should also take the Lumix. This is obviously a personal preference, but I have found I tend to appreciate photos taken with long lenses less and less. Anything I take with a long lens while on vacation seems like a photo I could just as easily find online, so what was the point? I prefer wider lenses up close to the action. The photos seem more intimate and better at capturing a unique moment in time.
I would seriously consider leaving behind the extra bulk of the FZ28, but fear of missing out would make it a tough choice. If you will be able to get up close to the action and fill the wide angle frame of your phone, I'm betting those turn out to be far more engaging photos. Not having the extra bulk and the worrying that would accompany the Lumix will make getting close that much easier. Not having so many choices afforded by a super zoom will let your mind stay in the moment and the photos will reflect that. The lack of a viewfinder with the wide-angle lens on your phone should not be too much of a problem if you don't rely on the screen anyway -- just point and shoot. Embrace the deeper depth of field, wide angle of view and the computing power of the phone. When the action is happening you won't have time to compose anyway.
On the other hand, if your ability to get in close is limited then that becomes the deciding factor in favor of the Lumix. In that case, I would bring the Lumix and use the zoom to bring me into the action rather than observing things from far away. Keep the phone handy for when things happen up close, especially when deploying the Lumix would mean missing the shot.
I have tried to learn to embrace making decisions about how I want to photograph ahead of time. Then I submit to the self-imposed restrictions and pick the minimum kit that supports that choice. I'd figure out what problem I am trying to solve first, and then decide on the gear to bring. Just try not to let the fear of missing out drive the decision (easier said than done).
