I think the key to this sort of predicament is to focus on items that can be served either with a large serving spoon or with a spatula. This narrows the choices--but does so reasonably I think.
I say this because, one, your're passing the service to others and it's easier for them to serve if the item is designed to be easily served from the get-go; two, narrowing the possibilities means you're not jumping through logistical hoops trying to make something work that would have been better left alone; three, it is easier to scale recipes or to figure out yield if you focus on how they will be served, and that's easier to do if you narrow the serving possibilities; and four, narrowing the possibilities helps keep you sane and thus more likely to enjoy the process (of supreme importance, imo)--something you'll look forward to.
The other thing to keep in mind is that if the food is going to be cooked ahead of time then reheated on site, it must be cooled relatively quickly then chilled till cold. If this is the case then it's obviously best to lean toward items that are more easily cooled, more easily reheated--or adapt recipes or procedures so that this becomes the reality; usually not hard to do.
One more thing, also for sanity's sake, is to make the hands-on prep and cooking more reasonable by limiting (at least to some degree) how involved you make your recipe. Individual meatloaves for 40 might be a bit much--but individual patties made with a meatloaf mix would be easy--and easy to serve.
Pasta and sauce is easy and easy to serve. (I prefer smaller shapes like rotelle, rotini, penne, et al., over spaghetti or linguini because they are easier to manage and easier to serve.) One can change the shape and change the sauce and go for months on the same theme.
Soups, stews, chili and the like are certainly easy to serve. (It important to figure out your cooling game plan up front--especially for thick stuff like chili or creamed soups as these tend to cool slowly in large quantities, opening the door for spoilage or food safety issues.)
Shepherd's Pie and other casseroles can be good, easy and inexpensive. An advantage to Shepherd's Pie and similar layered casseroles is that it is often possible to cook and cool the layers separately, assembling the dish after cooling.
The door is open wider if you can cook then hold hot, eliminating the need (and space) for cooling and refrigeration.