I never heard of the texting thing until it was posted here and a read up further and it seems teens were doing it because they were bored and isolated on Shabbos
Here is an idea instead of threatening them with stonning, how about showing them the beauty of shabbos (and others)
If you are a parent do you always threaten your children with punishment no matter how small the infraction, dont you try rewarding them if you do the right thing?