Um, the first thing that comes to mind is VISIT ME

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My mom stayed in a hotel off Kirkwood road, I'll drive by today and find out which one, lol. It's near restaurants, and Target, not too far from Whole Foods. I think it had a pool, and was relatively inexpensive. It's on Kirkwood rd near Watson rd.
The zoo is awesome! Try parking on the street before you pay for parking. We almost always find a spot on the street. Beware that the childrens zoo, insectarium, and railroad all cost money. IMO the children's zoo is worth the money, as is the insectarium. The railroad is neat because one ticket takes you around and you can get off at exhibits, get back on, and go to another spot. The downfall is that you can't use a stroller on the train. You're supposed to leave it at the entrance you first board, unless it's a single umbrella stroller. You can fold up and take those.
The Science Center is fun and interactive, and street parking there is also possible. I recommend parking free at the planetarium in Forest Park and going over the bridge over the highway (there is stuff to do in there, like radar guns to clock the cars, and windows in the floor to look down at the cars zooming by). That enters into the Science Center, which is mostly free.
We have membership to the Magic House. LOTS to do there, and up the street a little ways is a farmers market if you're iso fresh fruit and veggies. If you decide to do that, and want to meet up, LMK, we have free passes I could give you. I would love to meet up

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Grants Farm is well worth the money to park. The Budweiser Clydesdales are there. There are also, in addition to farm animals, elephants, a huge rodent that looks like a guinea pig (what is that called?), monkeys, probably others I'm forgetting. The free-range park has all sorts of stuff roaming around, and you ride right through them. You never know what you'll see. Plus, if your dh drinks (or you!), there is a hospitality Bud bar, with tap stuff, plus some of their bottled drinks (some sort of hard lemonade, yum!). You get 2 free drinks

. Might be an incentive, lol. My dh loves Grants Farm, lol. You can also feed the baby goats. Oh, and if you decide to allow one gift from one gift shop, make it this one. They have some really nice small toys, and they are not horrendously over priced. My ds got a stretchy rubber snake there for $2 that he adores.
The City Museum is absolutely fabulous, but my kids are just a bit young for it. I'd say age 5, younger if there is only 1, or enough adult hands, lol. I couldn't do my 2 there alone. It's really hands on, and the younger set would need lots of supervision. The cool thing is that they will have creations to bring home, so pack accordingly. There is also a glass blower on site, and he does demos. Really cool. The climbing area is the best ever, but again, for the older set.