My STBXW wanted to control all communications when she left. She said she thought it best that we present a "unified front" when we told the boys. My response was that we were far from unified, our kids are adults (well, early 20s) who are both out of the house and on their own (well...sorta...LOL), and I'm going to tell them the truth.
When my son came over one night and asked where she was, I told him that she had 'moved out', was staying with a friend, and told me she would be back in a week to tell me whether she wanted a divorce or not.
Of course, my STBXW gave me grief over that, said she had not 'moved out' but was simply 'staying with a friend.' I didn't respond because it does no good.
The next week she told the boys she had been unhappy for 20 years and didn't want to be unhappy for the next 20. I told them our marriage had highs and lows, certainly some rough times (as they were well aware), but I thought things had improved a lot over the last several years and that we could carry on ok if we both chose to, and that was what I intended to do, but if she chose to leave then I would accept her decision.
Of course, she acted like I was throwing her under the bus. I just made sure I gave them the facts from my side while pointing out that it was mom's decision whether she stayed or not.