Dan-- the mahi mahi idea sounds good. You could also pack a small grill (assuming you are car camping) so you can bbq some steaks. If you go the grill route, you could also pick up some polenta-- just slice it and grill it until golden/brown.
If you have a dutch oven or if you can get one, you could do a roast with vegetables--this is a super easy option and has the advantage of being a whole meal in one pot. Cut up an onion, some spuds, carrots, etc, and throw them in a ziploc bag. Throw your roast in another ziploc. When you are ready to cook, just toss the veggies and roast in the dutch oven and fill it up with water to cover the roast. Toss a few coals underneath, a few more on top, and let it simmer for a few hours.
As far as sides, you can bake potatoes in foil in the coals of the fire. Just make sure to poke a few holes in them before you foil wrap them so they don't explode. Another nice side is cous-cous. It's super easy to prepare. Just add a cup of boiling water to a cup of cous cous and let it sit for five minutes. fluff with a fork and serve. You can get plain, or many different seasoned varieties in the grocery store. Garlic bread is another easy one. Just wrap it in foil and heat it over the coals for a few.
--Josh