I live in St. louis! :) As for the Science center or magic house, the magic house is 100 times better, way more stuff to do. My almost 9 year old still loves the Magic House. The science center is one of those things that if you've gone before to all the free exhibits its boring the second time around and so on. The magic house you CAN not bring food in the place, but you can leave and come back in (same day) must see the front desk first though so you can re-enter.
The city MUSEUM is awesome, it is a lot of fun for kids and adults alike. Some places that the kids crawl through are dark, so bring a small flashlight for the kids just in case.
If you go to the zoo make sure to go to Turtle park after (right near it). Here are some pictures of it: http://playgrounddesigns.blogspot.com/2010/03/turtle-park-playground-st-louis-bob.html
Zoo: if you go early in the morning (first hour of opening) the carousel, children's area and 1-2 more things depending on the season are FREE. If you park close, you pay for parking if you park on the road short walk or long walk depends FREE. You can bring food into the zoo, no glass bottles.
I personally would skip Six Flags or put it on the bottom of the list. (But that's just my opinion).
Grants farm is sweet and I love it and so do the kids. Bring cash $1.00. You can feed the goats for $1.00 a baby bottle. Parking is $12.00 I think but its a super short walk otherwise there is free parking, but a longer walk. Some people have trouble finding the free parking, there is a path from the main street that leads to grants farm. Park on the other side of the main street, it's an empty gravel road next to empty land.
No experience with the Arch. (Bring change for parking).
I like the ABB, anheuser busch brewery a lot, I love the smell too! Fun Fun to go to. Short Won't last all day, not even half the day. There is also Shafley's beer. -Great outside/inside restaurant too.
My almost 9 year old loves the history museum Sometimes (depends on the exhibit).
There is also a Butterfly house, carousel and awesome playground park at Faust Park.
Edited by IcStarrs - 5/17/12 at 10:52am