Field Museum is a real time commitment — fit it in only if it's a priority.
Allow 2.5–4 hours.
A classic natural-history museum done at scale — SUE the T. rex, Egyptian tombs, and dioramas that reward a slow wander. The catch is the same as any big museum: it's a multi-hour, ticket-pricey day, and special exhibits cost extra, so families should pace it and pick a couple of halls.