No 2x4's from me today. I think you are teaching your children what Valentine's Day is all about and they should give their mother a card and the single rose is nice. Let the kids give her the card and the rose. She won't feel any pressure if they are coming from them.
They do tend to revisit the past quite often because they are searching for what they think that they missed. Listen to her, but don't offer up any comments and/or advice unless she asks for your input. Revisiting the past is one way that they are working on themselves and reflecting about what happened.
Being a good listener, friend and finding more patience is difficult, but you are doing a good job.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.