Help- Telling older kids- VERY Complicated

Hi. First time here. I really really need some help. My wife and I were married for 28 years. I was unhappy for most of it. My wife has really bad ADHD and often distorts things or insists on something irrational. I initiated the separation in February. Our youngest daughter is 20 and in South Africa for a semester and won't be home until June 9th. Our older daughter is 23 and fully launched. She lives in New York. She will be taking a graduate school admissions test the day after our youngest returns. She is extremely stressed about the test. We have not told either child that I moved out last February. I am extremely close to both kids. Being dishonest and evasive has been horrible. Both kids are aware of the stresses in our marriage. I have been the steady parent- making every meal, being at every event, always on time. I believe both kids see my wife as being very difficult to live with and have often had a stressful times with her. The oldest is coming home next weekend for an event. My wife insists I move back in for the 6 days our daughter is here and pretend that everything is normal. Then she wants me to move back in the week our youngest returns. The idea is that then we can tell both girls face-to-face at the same time. (If it didn't require this level of deceit, that would obviously be the preferable scenario). My wife is being very absolute about this, leaving me only two choices- move all my stuff back in for six days and lie to my daughter or drive to NYC to tell my older daughter by myself. I know that we should be telling our kids as a couple, reassuring the kids that we can still parent together. But I feel like what my wife is asking me is unreasonable and not the right thing. This is torture. Any thoughts, advice, help would be greatly appreciated.

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