Previous research has shown that children demonstrate similar sentence processing reflexes to those observed in adults, but they have difficulties revising an erroneous initial interpretation when they process garden-path sentences, passives, and "wh"-questions. We used the visual-world paradigm to examine children's use of syntactic and non-syntactic information to resolve syntactic ambiguity by extending our understanding of number features as a cue for interpretation to "which"-subject and "which"-object questions. We compared children's and adults' eye-movements to understand how this information shapes children's commitment to and revision of possible interpretations of these questions. The results showed that English-speaking adults and children both exhibit an initial preference to interpret an object-"which" question as a subject question. While adults quickly override this preference, children take significantly longer, showing an overall processing difficulty for object questions. Crucially, their recovery from an initially erroneous interpretation is speeded when disambiguating number agreement features are present.