You'll also want people to RSVP so you have a head count for the caterer. If, on the other hand, your rehearsal dinner will be fairly low-key or small (think: a party at a restaurant or an intimate gathering at your future in-laws' home) then you don't need to be as official with your invitations.
The exact nutritional value of an orange depends on its variety. According to the U.S. Department of Agriculture, a standard-sized navel orange contains 69 calories, 17.6 grams of carbohydrates and 11.9 grams of sugar.
One medium orange (approximately 154 grams) contains 80 calories, 0 grams of fat, 250 milligrams of potassium, 19 grams of carbohydrate (14 grams of sugar and 3 grams of dietary fiber) as well as 1 gram of protein.