Do you have a crock pot? A Pot Roast is a great dinner. Less expensive cut of meat. Pop in the crock in the morning and get home and its ready, leaves you time to do the sides. If you don't have a crock pot, you can do a long slow cook in the oven and let it go all day long-with liquid and maybe 230 degrees-my mom used to do it, but I don't remember the details.
Have nuts and sliced raw cheese for pre-dinner then I would do a nice big salad. The Pot roast, maybe roasted sweet potatoes. brussel sprouts, cauliflower riced, then cheesecake for dessert (it can be made the day before).
this site has a recipe for the brussell sprouts, the riced cauliflower, and a lime cheesecake. Recipe index « The primal recipe archive
for roasted sweet potatoes just peel and cut them (about 1 per guest) into 1" inch cubes put them on a greased cookie sheet into a 425 degree oven, till they are browned around all edges. How long sort of depends on how much moisture is in the potato and how big the pieces are, check at 20 and see if you can flip them, then you can judge how much longer to leave them in.
Lots of sides will distract them from the fact that there are no grains.