wedding audio

hi guys, im trying to improve my audio production for my wedding videos. at present i use a shotgun mic which i great but i often miss out with shy brides or grooms not speaking loud enough. i am thinking about using a lapel mic on the groom as well as the shotgun on the camera.

my question is - if i use a lapel mic on the groom and my shotgun mic on the camera together and the priest uses his own mic and PA system at the same time will the results be unsatisfacory. will there be any echos etc. i dont want to plug directly into his PA system, and i dont want long cables. I have read about the iriver option too but dont want to add to my post workload.

any help is apreciated.