Don't be so hard on yourself. Easy for me to say since I do the same thing as do most of us on here.
I would ask your boys if they want to give mom any other gifts and then assist them in getting them. The flowers you suggested would really be from you, and my opinion is that she would know that and it would give her another chance to twist it into thinking poorly of you. When she is in this fog it is tough because you can't do anything right in her mind.
Focus on you and becoming a great dad. Maybe get a book on parenting during a divorce. This is a critical time for your boys.
