If you do press on with this idea, Johnny don't buy a cover with heavily contrasting patterns....that always looks like grease stains are appearing on your laundry.
Make sure you get one that fits well...a wrinkly one is useless.... ;-)
Forget the lily water.....a family all smelling the same is on a par with matching bobble hats.
Wrap the ironing board cover in romantic paper....that will delight her but make sure you've left the house before she opens it and begins to steam....... :-)