If you want to 'fade' in peace....I wouldnt bring up doctrinal stuff at all. I suggest that you keep it mild but firm. Say that you have both been feeling very stressed with life in general and that you want to take time out for each other etc etc. They cant disfellowship you for that and if they suggest shepherding visits you can say assertively...'No thank you but no...we really want some space for now but we'll ring you if we need to .' Then whatever they say or suggest just repeat this. No brainer....they'll be stuck...wish to goodness I'd done this...long ago...
Loz x