The food is very similar to what you would get at Applebee's or Chili's. As for "worth it" that depends what you're into (I mean, some people think a signature restaurant isn't "worth it" because it's just food; and likewise, some people think it's worth paying a premium for the cool atmosphere at Sci-Fi even though the food is nothing extraordinary). The food is fine, but not outstanding. The experience is pretty cool. I agree, it's a "must do once." We're really happy we did it, we liked our meals a lot (onion rings, real cherry Coke, strawberry shake, shrimp pasta, mango glazed tofu, apple crumble, cheesecake with caramel corn and M&M's which was MUCH better than it sounds), the atmosphere was fun, we will probably never feel compelled to do it again.
You'd probably be OK with a 1-year-old if s/he's okay with it being dark, but your older kids will get more out of it.