Recording Latitude/Longtitude Coordinates of places for future descendants

One of the places that disappear are cemetaries. I have been asking around where the old cemetaries during colonial times were in our villages. Some people don't know and others have said that it is at a place where now a Church, rodeo or other structures exists today.

I would like to get a device or Garmin Etrex that gives you latitude and longtitude coordinates of the very spot you are at. So as to note it down. For in case of descendants in the future that do geneology research and want to locate certain spots. The coordinates would give the precise spot.