Meal for 30 people

Let's try the shrimp salad for the side dish, it would be really nice! :)
Check it at: https://lunaregina.com/shrimp-salad-recipe/

I have been in the same boat and thought for a long time about what would work! It's not the easiest thing to pull off -- especially because you want it to run smoothly and look under control. Here's a menu that has worked for me:

shrimp salad -- I recommend the following one, but I think it makes too much dressing -- and I would suggest making everything a day ahead but only tossing the shrimp with the dressing the morning of your party http://www.foodnetwork.com/recipes/ina-garten/shrimp-salad-recipe

chicken salad -- I recommend the following one, which you can make a day ahead, but any nice chicken salad recipe would be great http://www.foodnetwork.com/recipes/ina-garten/chicken-salad-veronique-recipe

a green salad -- make the dressing up to several days ahead and toss the salad together, minus the dressing, right before church

a spiral sliced ham (or two) -- bake it before church and then leave it on your counter

one or more types of quiche or strata -- bake them before church and leave either on your counter or in a warming bag of sorts (or you can serve room temp or re-heat for a few minutes when you get home) -- I recommend http://www.epicurious.com/recipes/food/views/spinach-and-cheese-strata-107754

some type of potato dish that isn't too mayo-y -- maybe a room temp salad like https://food52.com/recipes/29021-my-mother-s-potato-salad

nice rolls from the bakery

All of the above can be served in your fancy serving dishes (or not) and made to be more or less dressy, whatever your taste.

One of my favorite things to make for a crowd is a "fancy" taco bar. I slow roast a huge pork shoulder (I do it simply, but any number of spices would work nicely), and roughly tear it up and serve it along side corn tortillas, homemade pico, cilantro, limes, rice, black beans, cotija etc. You could have as many toppings or as few as you'd like. When I slow roast meats, I actually prefer to do it a day ahead and then let it slowly reheat.

Congratulations on your son's first communion!
Lasagna is always easy to make for a crowd. Depending on how far from the church you live, you may be able to throw it in the oven when you leave and pull it out when you get home. Or, if the weather is going to be nice, you could grill burgers and brats. They cook fast so no one would have to wait too long to eat.

I don't know how formal you want to be, but black bean chili reheats quickly. You can have diced or grated cheese, pickled red onions, chopped chilis and chopped cilantro on the side. Can serve w tortilla chips, salsa, and beer or Agua Fresca, maybe a relish tray. I assume Cake for dessert.