Need a bit more info ideally, is it lunch or dinner? Buffet or sit down? How many courses were you thinking? Any veggies or other dietary needs? The below ideas are for main course...
The easiest way of catering for that many is definitely some kind of stew-y thing which can be cooked in advance and reheated OR left bubbling gently away all day - chilli, curry, lasagne, moussaka, beef carbonade, coq au vin, pot pies, something along those lines. You can then do a variety of sides, both carby and veg. I quite like to do a venison casserole (venison makes it a bit more interesting than your standard beef or lamb but is no more difficult really). The casserole itself can be made the day before (gets better overnight) and then on the day make up huge trays of potatos, roasted veg, green veg, crusty bread etc.
The other thing that is nice for a crowd although more effort, is a huge roast, mainly just what you would do for the family but scaled up (as you have two ovens this should be OK with some pre planning), something like 2 big legs of lamb would be enough for 16 adults so long as not all enormous appetites, or would maybe stretch to 20 if some of those are children (or you have some veggies)? I'd marinade in garlic and rosemary the night before then slow cook it (if it's an evening do) so it's really meltingly tender by the time you want to serve. Roast potatos and veg can mainly be pre-prepared, par boiled and frozen then just finished in the oven on the day, leaving you to just need to do any fresh boiled/steamed veg.
Your other option could be to do BBQ if you have enough grill space? You could make it a bit easier and more interesting than the standard burgers and sausages by doing some big joints of meat (lamb shoulder, beef brisket or racks of ribs maybe), marinaded in BBQ rubs then started in the oven and finished on the BBQ. Do you have a slow cooker (or a nice big pan than can become a makeshift slow cooker)? If so you can do a pulled pork or beef brisket in the slow cooker to go alongside the bbq meats for very little effort. Again then some nice varied salads, nice bread, coleslaw, maybe chips or potatos etc to go alongside?