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.
However, orange juice can be fairly high in calories and carbohydrates if you don't watch your serving size. One 8-ounce cup has 112 calories and almost 26 grams of carbohydrates, so if you drink a large 20-ounce glass of orange juice, those numbers go up.