Based on N of several hundred, restaurants can generally do a pretty good job of banquet-style serving for large groups by using a limited menu and keeping things simple. It's probably not quite as good or as customized as ordering off the menu, but it can definitely be serviceable or better.
Catering a meal for a large group is tougher without a local kitchen. If you're imaginative about meal choices (e.g. optimize around BBQ of some sort) or if you're willing to tolerate lines for e.g. food trucks you can do better. But in my experience you have to make some choices to serve a large meal where there's no permanent kitchen. (I did work for a caterer once upon a time.)
Catering a meal for a large group is tougher without a local kitchen. If you're imaginative about meal choices (e.g. optimize around BBQ of some sort) or if you're willing to tolerate lines for e.g. food trucks you can do better. But in my experience you have to make some choices to serve a large meal where there's no permanent kitchen. (I did work for a caterer once upon a time.)