I’d rather suggest you to use a full-GIS software to achieved your goal. A viable solution is to create a vector grid using for instance QGIS (in particular the MMQGIS plugin, see e.g.: http://michaelminn.com/linux/mmqgis). Then, convert back the resulting shapefile grid into KML (see e.g.: http://www.townshipgis.com/resources/problems-and-workarounds/convert-shapefiles-to-kml).
Also for sampling work, you might have more flexibility to perform it within QGIS directly on the shapefile grid instead of using G. Earth.
Very late to reply this question but here is a link to a Google Earth Engine base App to generate grids (that can be used for Collect Earth or other ends ): https://collectearth.users.earthengine.app/view/collect-earth-grid-generator
It is important to mention that should set the right EPSG code of your area of interest in order to get the most exact distance between plots.