J.R.
Casa Bonita is definitely fun but the food is worse than Chuck E Cheese!
If you want Colorado kitschy, we really like the Trail Dust which is close if you are in Westminster. It's in the parking lot of the Westminster Mall on the east side. Plus if you're new to CO, then you have to go - it's a Colorado tradition!
They are a steak and ribs place that is yummy. The texas toast is well known in the area. Big huge tables and family style sides. They usually have music playing (yes country western) with a dance floor so you're little one can dance. Very family friendly.
There's a HUGE slide that my boys just love to go down (and adults are allowed down with little ones).
The funniest thing about the Trail Dust is that if you wear a tie, the wait-staff makes this big hulabaloo with cowbells and they come over and cut your tie off! Then they hang the ties on the wall (the place is covered with them) and you get a free drink. My kids have gone to birthday parties there and the parents buy a bunch of thrift store ties just for the ocassion.
Of the three, that's what I'd pick!