You can do the Arch, Science center and baseball game in one day. One day for Six Flags, one for the zoo and one for the City Museum. The arch and Science center don't take very long. The zoo, Six Flags and the City Museum take a lot of time. So those things would consume all of your day. The zoo is free to get in. You can park on the street for free or in the parking lot for like $10.00. I never park in the parking lot so I'm not sure about the price. If you want to do some extra things in the zoo some cost. The childrens zoo area for young children is $4.00 and the train is also $4.00. You can have a great time and not spend a dime. You can also pack your own lunch and drinks to bring in.

Six Flags has coupons on Lunchables (on the inside) packaging for $4.00 off adult admission and free child admission. So it would be $24.99 plus tax for each adult and the child gets in free. Also, Schnucks grocery stores sell tickets usually cheaper than at the gate. You can also pack a cooler and lunch and eat outside the park for much cheaper than in the park. You are not allowed to bring in food or drinks other than a bottle of water.

The Science Center is located close to the zoo. If you enter through the Forest Park entrance you do not have to pay for parking. The Science Center is free also unless you want to do some of the extras such as the Imax. The Monster exhibit they have currently is not worth the money so don't do that. You can enjoy the whole thing without having to spend anything.

The City Museum I believe has a coupon on the St. Louis Attraction website that was posted earlier. I don't remember their prices.

I'm not sure of the best places to stay in the city. I would check tripadvisor.com for reviews.

Enjoy!!