Messenger Bag or Panniers

The question of the week...to go with a messenger bag or panniers for bike commuting? I've been using a messenger bag for a few weeks now, and although it is very cool looking, I am wondering about the long term practicality of it. It is quick and easy to stuff the normal commuting items like a change of clothes and lunch, throw it over my shoulder and go. However, it can get old always having the bag on your back. Panniers would allow me to let the bike carry the bags and get the load of my back. With panniers, though, the bike has to be outfitted with a front or rear rack to accommodate them. This probably wouldn't be a big deal since I usually only commute with one of two bikes. One already has a rear rack, and the other one can easily be fitted with one. There is the added time of removing the pannier, but that shouldn't be a big deal, either.
For simply commuting I don't think it makes much difference which way to go. I'm thinking more long term...things like going out for longer rides and wanting to bring along a few things. This would get rather uncomfortable with a bag on my back. I'm also daydreaming about some short touring adventures, hopefully with the family. This would obviously favor panniers over a bag.
As I write this, the panniers seem more and more like the right thing for me. Now I just need to figure out a way to unload my messenger bag and score a pair of nice panniers.

Slow Ride

On New Year's Day I went for a bike ride...all of probably 1 mile, and it was great. What made it great was not how far I rode, but who I rode with. My whole family went riding at a nearby lake. I was on an old Schwinn 5 speed, my wife on her old Trek mountain bike, my 8 year old daughter on her first "real" 2 wheeler, and my 6 year old son on the hand-me-down 2 wheeler with training wheels. We just rode the short distance by the lake on a relatively flat paved trail, stopping at about 1/4 mile to feed some ducks. Then we proceeded back and stopped at another spot to feed more ducks. We then rode about another 1/4 mile to another area to again feed the ducks and have a little snack for ourselves. Obviously, the riding of bikes was not the main objective of this little outing, spending time with the family was. It was nice getting outdoors on a fairly mild day and actually doing something together.
Part of me cannot wait until the kids are old enough to really go on bike rides with me. Yet, I also don't want them growing up too fast. For as much as I love riding, we don't seem to be able to all get out and ride together as I wish we did. Maybe investing in a tag-along bike or tandem would make it easier? We have a trailer, but the kids have just about outgrown that. Anyway, even these little riding adventures beat sitting around the house watching TV or listening to the kids argue over everything. Now I just need to make sure we do them more often.