We grill a lot on our boat, but then again we also grill a lot at home. Be careful of murphys law when grilling. If there is little wind and you break out the grill be prepared for the most wind you will have all day.
Good insulated cups with lids are great. We also found some deep bowls that work well for serving things like fruit.
We always keep crackers and graham crackers on the boat. It is always good to have extra snack food on the boat just in case you end up being out longer than you anticipated.