Walmart and the like sell sets of little tiny stickers that can be fixed to the back or center of a DL. Someone I know the Casino made her remove the sticker claiming that the ID scanner would not accept the sticker on the face (wording: "without prejudice") Alternatively, making very small, illegible marks via the signature pad...ya know...just a dot or two for a 'signature' an then using a fine magic marker to finish it off once the DL comes in the mail...well u get the idea.
Removing the laminate temporarily and writing directly on the plastic card is perhaps an option?