Do not be nervous about California Grill. There is a suggested dress code of resot or business casual there, which is collared shirts, pants for men, they do not allow swim wear/pool wear, ripped clothing etc. I have never seen anyone turned away, but wearing a swimsuit is inappropriate in a restaurant to me. Polo shirts, khaki pants, dress shirts, tank tops for women, capris are the norm, some people come a little more casual.
There are some basic meats like the pork tenderloin and filet, both are wonderful. If there is a specific ingredient that is added to the dish you can ask to have it omitted, unless it is part of a recipe that they cannot change. You can also request a different side dish if you dislike the one it is served with. Try a couple of appetizers or salads between you and make him try something new. The flatbreads are delicious. The food is really great, I do not think you will be disapointed.