At the tiled wall, when we grout the tiles, should we leave it out around the receptacle box?
You want to fill in all the grout lines under the cover plate. Don't worry about that last tile edge next to the outlet box and don't fill in all the space around the box. If the distance between the face of the box and the finished wall is greater than 1/4" then box extenders are needed. Enjoy your new kitchen.