My youngest boy is riding in the BMX Grand National Races (the biggest BMX race in the world). This is an annual thing in Tulsa and we'll be there for four days on Thanksgiving weekend. We'll have a lot of down time between races and I need to come up with some reasonably priced activities to distract the wife and two boys (5 and 7). We're staying slap in the middle of downtown, so if anything is within walking distance, that's great. If not driving is fine too. In a quick google I came up with the following:

Gilcrease Museum (for the wife and I, the kids would just have to suffer through it)

Tulsa Zoo

Tulsa Air and Space Museum

Any other cheap or free things to do for a family of four in the Tulsa area? Thanks guys.