Translation:The children walk off the carpet and play beside the carpet.
If I am not mistaken,it is not plural. If it were plural it would be "szönyegekről" the second part of the sentence uses the word carpet without the suffiix meaning off from, and adds the adverb mellett for beside for modifying játszanak.
My problem with this sentence is that when I see sétal I think of actual walking, like taking a walk, or walking from one place to the other. A better word here would be that the children step.= lép etc. Do you agree?