I wouldn't do it. In your own words, they haven't been nice tenants. Why do you have to put yourself at out of time and more importantly money, for them? They aren't your best friends.
Tell, them that you won't be able to extend the lease because you have a new set of tenants already moving in. Plain and simple. Don't bother with explaining to them all the extra costs that they will have to cover such as the lawyers feee, and paperwork processing etc. That will ignite them to possibly damage the unit before they move out.