Hosting a large family gathering in Houston – what should we do?

I live in the Cypress areas and I'm hosting some family for a week in July. Total count is 6 adults and 6 kids (age 4-12). What should we do? Help!

Considerations: 2 kids are pretty young (4yr old). Cypress isn't the best home base for touristy stuff – everything seems kind if far away. Outdoor activities seem dicey – you know, Houston in July. I'd love to give them a "Texas" experience once or twice because they all live on the east coast. And go….