On top of the size of the room issue, is this system only for background music while the kids are eating? I’ve been in school cafeterias during lunch time, and the din from everyone talking and carrying on is tremendous. I can’t imagine trying to play any kind of music on top of all that.
On top of the previously mentioned fire and electrical codes, there is the safety issue of running all the required wiring. It can’t just be strung across the floor where kids can be tripping on it or playing with it (you didn’t mention the age group involved). On top of that, if the speakers are of the size that’s probably needed for a large room, and are going to be hung on the wall, you have to know how that is done properly to insure they aren’t to fall down.
Bottom line – unless you know how to do all this stuff yourself, you’d best hire a professional sound company.
Regards,
Wayne A. Pflughaupt