I love natural history museums, and this one definitely did not disappoint. My kids (7, 5, and 1.5) all had fun experiences. We did the general admission (which was free with reciprocity from our membership with one of our hometown science museums! If you have a museum membership travel with your card to check for reciprocity; it saved us over a hundred bucks this time). We were at the museum for just under 5 hours and didn't see even a fraction of the displays There was so much included in the general admission we didn't feel the need to pay for any additional exhibits at all, although when we purchased our tickets they told us if we came across an add-on exhibit we were dying to see we could always come back and pay for it at that point (which was a good tip).
A few tips that were helpful for my family, if you're planning to tackle the Field Museum with little kids:
1) A parenting blog I read recommended using the east entrance because it's stroller accessible and has shorter lines than the main north/south entrances. That was such a great tip! We arrived at 10 AM on a holiday Sunday and walked right in. We didn't have to wait even a second in line.
2) You can bring your own lunch and there is a spacious cafeteria on the ground level with a bunch of vending machines. We packed sandwiches and fruit and then bought vending machine chips and cookies as a treat. Everyone was satisfied and we saved $$$ not paying for lunch at the museum cafes.
3) SUE was amazing to all of us. The exhibit to get to the hall of dinosaurs is fascinating, but long and winding so don't think that SUE is something you're just going to pop in and out and see. You have to walk a while. Definitely worth the trek, though, and you'll learn some cool things along the way.
4) Our other favorite exhibits were ancient Egypt and the rooms featuring Native American cultures. My kids really enjoyed the exhibits featuring the replica Pawnee meeting house and the pueblo. I actually think they liked that exhibit more than the dinos or animals, which was surprising. We enjoyed the gem stones and meteorites and the "What is an Animal?" exhibit as well.
5) On the ground floor right near the cafeteria is a playlab. I actually didn't think it was that fantastic in comparison to the rest of the museum, but clearly I'm not the target audience because the kids were big fans. Their favorite thing was (another) replica of a pueblo with an area to harvest pretend corn and pretend to grind it and cook it. I think playing imaginary games there was their favorite part of their museum day. There was also a room with instruments that was a huge hit with my toddler and areas to play with microscopes and all sorts of manipulatives. It's honestly nothing you won't have seen in a hands-on children's museum before, but it's a good spot to stop before or after lunch to burn off some energy before going into more serious exhibits.
All in all this made for a great family outing and I only wish we'd had even more time to explore.