Steve, I have been an assignor, and have found that most coaches will let the umpires drive to the site and try to talk them into playing. A little proactive action on our part can save time and foolishness like this

Gunga Din
 

Well God bless ya and all, but I've never heard of an assignor calling the coaches to see if their fields are ready. The assignor's job is to assign officials, and to notify officials of changes. If you go as far as checking in with the coaches (who should be checking in with you), then you are in a vast minority of assignors.