When they're running with the wind in their faces and the sun on their backs, or stepping barefoot onto cool, green grass.
( ( When ( they ( 're ( ( ( ( running ( with ( ( ( ( the wind ) ( in ( their faces ) ) ) and ) ( ( the sun ) ( on ( their backs ) ) ) ) ) ) , ) or ) stepping ) ) ) ) ( ( barefoot ( onto ( cool ( , ( green grass ) ) ) ) ) . ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (PRP they)) (VP (VBP 're) (VP (VP (VBG running) (PP (IN with) (NP (NP (NP (DT the) (NN wind)) (PP (IN in) (NP (PRP$ their) (NNS faces)))) (CC and) (NP (NP (DT the) (NN sun)) (PP (IN on) (NP (PRP$ their) (NNS backs))))))) (, ,) (CC or) (VP (VBG stepping)))))) (VP (VBP barefoot) (PP (IN onto) (NP (JJ cool) (, ,) (JJ green) (NN grass)))) (. .)))
They are having a barefoot race. 
( They ( ( are ( having ( a ( barefoot race ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (VP (VBG having) (NP (DT a) (JJ barefoot) (NN race)))) (. .)))