The restaurant on Paradeplatz is a sure bet as are essentially all of the establishments in the Movenpick chain. They generally offer a good selection of meals at reasonable prices for even the pickiest of eaters (and believe me, I am one!). This particular Movenpick is a bit more upscale than others across Switzerland but it can still be considered casual dining, although I wouldn't recommend cut-offs, a ripped tank top, and flip-flops as proper attire!
If they are still on the menu, I personally recommend the three cheese ravioli, but don't forget to leave room for some of Movenpick's heavenly ice cream; it's quite possibly the best you will ever taste!