Other than the smoke (which didn't seem too bad) it would be fine for kids, and as you walk in (park in the back lot), they might be amused by the stalls for the vendors. Really good hamburgers, good tenderloin too.
Thanks to everyone who posted! As a self-proclained foodie I love this site but wish there were more KC posts or even a KC forum all unto itself. We will try WFM soon with kids - I have a 7 yr old cheeseburger afficiando (sp??) so we'll be sure and give her review here soon.