Corrine, What an absolutely lovely thing to do!
Here's a very basic simple prime rib recipe -
SIMPLE PRIME RIB ROAST
12 pound Prime Rib roast, at room temperature
Salt and freshly ground pepper, to taste
Preheat oven to 425 degrees.
Season roast with salt and pepper. In a roasting pan place roast, fat side up, so that ribs of roast act as rack. Roast for 30 minutes and reduce heat to 350 degrees. Continue to roast for 2 hours more or until meat thermometer registers desired doneness. Transfer to platter and let rest, covered, for 20 minutes.
For the pan sauce:
2 cups beef stock or canned broth
Sprig of thyme or 1/2 teaspoon dried
Worcestershire sauce, to taste
Salt and freshly ground pepper, to taste
Skim off fat from pan drippings and add stock and thyme. Bring to a boil and simmer 10 minutes. Season with Worcestershire and salt and pepper to taste.
You can add some roasted garlic to the pan sauce for added flavor.
For the roasted potatoes, you can just peel some baby new potatoes - red or yellow, and put them right in the roasting pan for the last half hour or so - they get 'basted' with all the meat juices; or roast them in a separate pan, with some oil, salt, pepper.
For other sides - a traditional New England side with prime rib, do some stewed tomatoes - used canned whole tomatoes, add a little onion/celery, and a little brown sugar, and cook slowly til the tomatoes break down; it should be thick, but still a little runny.
A simple succotash of baby limas and corn, with maybe some chopped red bell pepper for color, some green beans amandine, maybe a salad? And rolls.
I'd kind of keep it on the simple side, for a number of reasons; firstly, easier on you! Secondly, I'm not sure the folks you're serving would know what some of the more 'exotic' dishes were, so keeping to simple, hearty nutrition might be the best way to go here.
