That can trigger all sorts of feelings and images that are hard to scrub from the brain.
You might want to tell them for a number of reasons, set the ground rules first.
Help each other understand what you are trying to achieve by this conversation and if one of you objects, see if there is another way to convey the information without details and maybe at a more conceptual level.
"You know what I would like to try?" versus "When I did this (specific behavior) with my ex, I really enjoyed it."