I have a 4 year old and a 1.5 year old.
Sledding is great for our 4 year old, but his younger sister can't stay out too long. Hopefully next year we'll fare better.
I hadn't heard of the Lookout Ridge location:
Lookout Ridge Indoor Playground
For Tues and Thurs it looks like it only costs $3.50 after 6pm.
I'll have to check that one out.
There are fun play areas at the Maplewood and Rosedale malls as well. And those ones are free.
Children's museum is a lot of fun. They have the Target Free Sundays (3rd sunday every month). It's free, but it's nuts. Try to go on a weekday or any other day for that matter if you can't handle HUGE crowds.
Sometimes we'll go for a cheap breakfast at IKEA and then my son can go play in the ball pit/children's area for a while.