If a living tree falls, it is covered by your homeowners, if a dead trees falls it is not covered. I would be safer to take them down. They will rot at the bottom and can fall and other problems will rise. If you have some who makes things from wood this would be a beautiful to do in ASH, or use the wood on your property, sell it, call a lumber yard and have it made into wood boards for paneling. short trees could be left for woodpeckers.