As mentioned, picking a good route is a lot of work. Not all states have traffic volume data available. I'd aim for the paved roads that are the remotest. In a lot of places, county highways are a good compromise; they are more likely to be paved and have lighter traffic. Ken Kifer has a good section on how to interpret maps, see http://www.phred.org/~alex/kenkifer/www.kenkifer.com/bikepages/touring/maps.htm
You can check the condition of individual roads with Google Maps street view. It will tell you the general condition of the roads, and whether or not there are paved shoulders. You can also find bike/multiuse trails with Google Maps; go to the desired area at close zoom, and click Directions and the bicycle icon. Green lines will appear on the map for paths open for cycling. And the roads that are recommended for cycling will have green dotted lines on them.
If your group has a lot of inexperienced riders, I'd make double sure to use low traffic volume roads. And get everyone to read the PA Bicycle Driver's Manual (http://www.dot.state.pa.us/Internet/Bureaus/pdBikePed.nsf/BikePedHomepage?openframeset&Frame=main&src=InfoBikeManual?readform
), especially chapters 2-4.