Things to consider as you compost manure:

• Weed seed content (including noxious ones)
• Pesticide residues (especially ones for controlling broadleaves and noxious weeds on range or pasture). Some of these can persist in the manure for up to 18 months!
• Pathogens (E. coli, Salmonella, and Campylobacter bacteria)
• Salts and heavy metals (excess salts can burn plants)
• Nutrient content (manure is relatively low in N, but can be very high in P and K)
• Feeding livestock purchased hay or hay from on site (potential weed or pesticide content)
• Veterinary pharmaceuticals
• Also, related to food safety, they should wait at least 120 days after applying raw or aged manure to harvested crops that grow in or near the soil (root crops, leafy greens, strawberries) and wait at least 90 days for other crops.

Composting manure for several weeks at 140°F can solve several of these issues by killing the weed seed and pathogens (not including herbicide residue or heavy metals).  I have included several links below that I found online.  You could just reference some of these documents and resources in the flyer, so people are responsible for doing their own homework.  I think it would also be a good idea to encourage testing of soil and manure prior to application if any of these issues are of concern and for application rate information.