I did want to mention something I came across in one of the Sidney Sheldon books I read recently.
They mentioned how one character would leave little notes in various places in the apartment for his girlfriend to find. The notes would be in the bread box, refrigerator, dresser draw, etc.
So my challenge for you, and it should tie in with Christmas too, is to go to the Hallmark store and buy a few of those 'cutsey' type memo pads. The themes should be varied, maybe one or two really 'hot', some romantic, and a few 'cute'.
Then each day you are to place a note or two in a place where you know your wife will go that day, so she will find the note. The notes themselves can be anything from reminding her of something she was going to do, maybe telling her you will be doing something she asked you to do or maybe just a note to tell her how sexy she is.
You did not mention what you got her for her birthday, but some of the notes can be along the lines of Santa's list has a special entry for you and the thing is bigger than a breadbox.
The point is the notes are not to be one specific type; some should complement her, some challenge her, some might be apologetic, and others might share a joke or something about one of the kids.
They will always be found in a different place, use different paper, and hopefully over the long haul, show that you are really thinking about her both by the content of the note and the place it is put.
For example if you know she is having a special meeting or something to so with work on any given day, you might wish her well and leave the note on the visor in the car.
The point is as opposed to my major bath time approach, this is a little at a time approach that actually requires you to show that you are thinking about her.