When we used to camp with the kids, I would fill two-liter plastic bottles with water, freeze and cap. Use those in the cooler and they keep food colder for longer, plus you have fresh water to drink or cook with when they thaw.
I would, at a minimum, buy a stove-top percolator. Coffee is NEVER better than when perked and enjoyed outdoors in the early morning. A Dutch oven is a good multi-purpose implement, particularly if it's one of the old style ones with the lip and legs, so you can set it in the coals and pile coals on top. You can cook about anything in that, up to and including baking bread. It would be worth buying one of those should you happen across it at a thrift shop or some such.
If it were me at this stage of my life, I'd probably make up some single-serve meals and package in foil pans, freeze and take with me. Won't hurt them to thaw as long as they stay cold. The pans can go in the coals or on the grill, or inside that Dutch oven. Big baker potatoes and canned chili or stew are a good choice, too. Wrap a potato in foil, nestle it in the coals, let it bake, split it, top with chili or stew. Fine dinner.