Echoing what a previous poster said: don't bother with the food inside the park. Except for...
...their famous fried chicken! SO YUMMY! The boysenberry punch is also good, and something you can't get anywhere else.
If you'll be there on a weekend before the end of summer, they've got a great special going on. For $39, you can get admission + an all-you-can-eat meal that includes the famous fried chicken, plus bbq, side dishes, desserts (boysenberry pie!) and soft drinks. That's alot less than just the cost of admission regularly; here's a link to a coupon:
http://www.knotts.com/bbqspecial/
Also, since you don't care for rollercoasters, there are other things to do. There's the Wild West stunt show (held in an outdoor theater made to look like a wagon camp, with covered wagons that you can sit in to watch the show). And the steam train that goes around the park. There's the "Ghost Town" section of the park, that's part of the original Knott's park. And Bigfoot Rapids, a GRR-type water ride that's fun on a hot summer day! Unfortunately, the Haunted Shack is gone now- that was a classic; don't know why they took it out.
Have fun on your trip!