I would just eat it. Col slaw is safely edible for ages after the 'best by' date. The mayonnaise contains vinegar which is a preservative.
I dislike bought mayonnaise, it always has far too much mayonnaise or dressing or whatever it is.
I prefer col slaw French style, just enough dressing (often not even mayonnaise), to hold it together slightly and no more.
I've got another 'keen'... Ouch!