Fruity, I applaud you for having this discussion with your teen children!
As for updating Wills, this is a separate issue. You can find the forms for your state on the net...download, print, and execute them. They are not part of your Will (which we know from old movies could be read months later <g>).
In addition, you might want to consider a DNR.
And finally, imo, it is best to put your wishes in writing for disposition of your remains in an envelope taped to the front door jamb...altho many seem to prefer the freezer for such docs. ;-) Point is, you want those wishes (along with your Directives) easily found and read, should they be needed in any situation including an emergency.
Example from my state of California:
There are two basic kinds of health care documents: the Durable Power of Attorney for Health Care, naming a trusted person to direct your health care if you are unable to do so yourself, and the Living Will, setting out the types of medical treatment you would or would not like to receive in certain situations. You can also specify who you would is authorized to direct the disposition of your remains. In California, these two documents are combined into a single form called an Advance Health Care Directive (AHCD).
More here:
http://www.saclaw.lib.ca.us/pages/living-wills.aspx
I am not a lawyer so this post is meant only to suggest to its readers that you check your own State law and consult with an atty re your personal concerns.
~jmo~