all homemade--no ready made crust. Will they be soggy if frozen after baking?
You cannot make reheat frozen precooked quiche without some loss of quality, particularly the crust as you fear.
You don't mention if it's a football tailgate, a paid function or a wedding so there is zero context into your audience.
Make one quiche, freeze, thaw, and reheat and verify yourself if the end product is something you will want to serve for those 150. After all, your name is going to be on it, you're the one who should decide if it's acceptable for *YOUR* standards.
If you do not find the trial run to be acceptable, find something else for the group.
I worked at upscale, high volume brunch restaurant, and our pastry chefs would par bake the crusts (keeps them nice and crisp), then freeze the crusts. Then up to three days before service they would make the egg custard with whatever was seasonal from the restaurants farm, cook them in the crusts from the freezer and than refrigerate before service. I would then cut (much easier when cold, less breakage on the crust) and would reheat each portion on a sheet pan in a hot oven for about 10 minutes. We then served them with mixed green salad, and the quiche was always delicious, because the flavors had melded so well and the crust remained crispy. So doing your crusts first, then freezing after a bake bake, a few days ahead make custard, fill, and cook off, cool, cover with plastic wrap, cut day of and reheat on sheet trays. I hope this helps. I would avoid freezing the eggs mixture as it loses its light texture. Happy cooking!
I agree. Freezing the crusts and filling them later is the best compromise.