From memory, the last time I did Viper - Three Elms (via Chequers Inn @ Roxwell ), its a bit tricky to get a route to Three Elms without retracing it on the way back unless you head up Roxwell Road to Easter's and then back down... makes for a longer ride though... Also - whilst the road surface is good from Ivy Barns towards Viper, it gets worse once you come round the left hander with the gravel driveway on the right. Probably fine with the fatter tyres of the CdF, but quite unpleasant on 25mm/Carbon frame.
My usual route to the Viper would be through Stock/ Ingatestone / Fryenning but that would be more miles for you guys? You could go Watchhouse Rd/London Hill / Swan Lane (if you fancied more climbing) or Danbury /Bicknacre / Hanningfields
Less pleasant route running in to Ingatestone via Stock Lane:
https://connect.garmin.com/modern/course/10394090More Pleasant alternative would be to turn left and head in to Ingatestone via Buttsbury & Padhams Green Rd. (includes a ford for those wanting a paddle...) (about 3 miles extra but less traffic and nicer lane)