Threesome

So my husband and I have talked for over a year about having a threesome with another lady. Our friend was down then changed her mind because she was afraid it would change our friendship afterward and we totally respect that decision. My husband gets stressed easily and thinks meeting someone will be too stressful but is okay with me trying to meet someone. I’m curious if anyone has gone through this. I’m afraid me trying to meet someone without him involved in the meeting process will feel like cheating and I don’t want either of us to feel like that is happening. Just wondering if anyone has any advice