"Resort casual" is their stated dress code. I believe this means they might frown if you were to come in wearing swimwear & a cover-up, a torn t-shirt and ripped cut-offs, etc. Most of what you'd wear to the parks is fine. I've seen people who were more dressed up, but for the most part what I've seen is what most people would consider casual dress for work.
If you have a PS, the guard at the gate will have it on a list. They might give you a parking pass -- but then again they may not. You can also valet park for $6 (plus tip). You should have no problem getting to the restaurant that evening.
Have a great meal (I highly recommend the cedar plank salmon with the berry cobbler for dessert. You'll probably need to be "wheeled" back to your car, but it is so good and so worth it!)