Damien’s Invitations Have Gone Out

So now fifteen of his school friends have been invited for movies and pizza (so far it’s pizza- he may change his mind) on Saturday April 8th. He came up with some beautiful invitation ideas and I did them on my laptop for him, several different dragon pictures with the invitation written over them. They came out really nicely too. They were about A6 size- but before I could finish them nicely he had cut them out and taken them to school! So. If they all come over on his birthday- I’ll have sixteen grade eight teenagers in my living room. I did specify RSVP at the bottom with my number- since none of them have been here before and will probably need directions- but people don’t seem to do that anymore, RSVP I mean. Even if you don’t specify RSVP you still don’t get a “Yay” or “Nay” from anyone and I find that exceptionally rude. Even a little text message acknowledging the invite would be enough. I haven’t heard from one of them or their parents yet.
Is this something that is acceptable in society nowadays? That you need not acknowledge an invitation- let alone RSVP!?