A good place to start is the bdsm checklists which you will find here and online - lists of various practices and toys which people can rate on a scale from "WOW!" through "maybe" to "NO WAY!" The three of you could get together and fill out one each, in a cosy private setting with drinks and nibbles, so instead of being heavy and scary it's like a game where you can laugh and share and say "Does anyone really...?" and "I've always wondered what that was like..." And then compare the results and see what you all want to try.