Rather than trying to please your mother, think of how you can make it easier for her (and that will mean its also easier for you). Keep it low key, don't talk about it again, and focus on the fact you are doing the best thing for her.
I didn't discuss it with my mother at all. I asked the care agency manager to ensure my mother's carers didn't talk about it until the morning she was moving, because I knew she would get in a complete tizz about it, and in particular about what would happen to her cat (I rehomed him). On the day, the carer told her she was going on a mini break near me (I live by the sea). Moving to a care home is always going to be challenging, but there are ways of minimising the distress. I had two months of hell making the arrangements, I didn't want to have to spend half my days calming my mother down as well!