Lid hygiene ( J& J baby shampoo scrubbing,with an antibiotic ointment twice a day as per your ophthalmologists advice,with warm water compresses at least for a period of 30 days) is what is going to keep the recurrent Styes away from him.
Yes, children who rub their eyes often after exposure to dust are definitely more prone for recurrence.
And do rule out any refractive error
on your next eye checkup .
Hope he feels better soon.:)