If you really want to do the dinner there are some things you can do to speed things up.
1. Let your server know you have a PP cruise booked.
2. Have an idea what you are going to get before you enter the restaurant.
3. Order your meals and drinks the first time your server arrives.
4. If you are planning on dessert order it when you entrees arrive.
5. Ask for the check when your meal/dessert arrives.
We have never been in a sit down for more than about an hour. but then again we don't order drinks, apps., then entrees, then dessert then after dinner drinks, etc. We get in, order, eat and pay the bill then back to the park.