Had child write what they wanted to be on the rock. Here she chose her name and some hearts and a butterfly. Can let them use a pen 1mm, or a sharpie for thicker results. 

Next. I just placed the sheet into my printer/scanner, and used Document type at 300dpi. 

I then saved the photo as a JPG

I then opened the photo in Adobe Illustrator and cropped the image to just the handwriting.

Select the image open the Image Trace. 

Silhouette is a good choice. I used Sketch on the image trace though to fill in the heart more.

You should now be able to drag the image to the side, and it should have no background.

Now click File, Export, Export As.

You're going to Export As an SVG file.

And Save

Next. Open Xtool Creative and Import Image.

You going to open the SVG file that you saved it under.

And I just used the Rock Coaster setting for the engraving.

Frame it and Engrave it!