It's good to see that a police department is trying to be sensitive to the fact that government cannot favor one religion over all others, but rather than playing roulette with pastors since some don't want to give a nonsectarian invocation, wouldn't it be easier not to give invocations at all? Even non-sectarian prayer, after all, excludes non-believers.
MORE: http://au.org/blogs/wall-of-separation/law-enforcement-nc-police-chaplains-told-not-to-invoke-christ-in-official
See also...
CMPD chaplains told not to use 'Jesus' in official prayers
http://www.charlotteobserver.com/2012/06/21/3331333/cmpd-chaplains-told-not-to-use.html