If you do not know death date, but know the location they died, you can enter that and it will remove the "living" protection on the ancestry tree. If you know they are dead, but do not know the location or date, you can change the setting on ancestry.
If however, you do not know if they are dead, as you mention in your OP, you should leave the "living" protections in place on ancestry.
If however, you do not know if they are dead, as you mention in your OP, you should leave the "living" protections in place on ancestry.