ضَاحِكَةٌ مُّسْتَبْشِرَةٌ
Sentence structure
Both words are feminine-singular nominative active participles describing the faces in ayah 38. They may be parsed as further predicates or as adjectives.
Ayah summary
They will be smiling and rejoicing.
ضَاحِكَةٌۭ — Laughing
Grammar: A feminine singular nominative active participle describing وُجُوهٌ; it may be parsed as a further predicate or an adjective.
مُّسْتَبْشِرَةٌۭ — rejoicing at good news
Grammar: A form X, feminine singular nominative active participle describing وُجُوهٌ; it may be parsed as a further predicate or an adjective.