On a budget, weigh it — Field Museum isn't cheap for what it is.
$30–40 adult (basic)
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.