G.G.
My family is big on parties so I've been to a million of them at various places around Chicagoland. The ones I would recommend are:
Pompei Bakery http://www.pompeipizza.com/
Marcello's http://www.marcellos.com/
Nikos http://nikosrestaurant.com/
Grotto Oak Brook http://www.grottooakbrook.com
I would also recommend Maggiano's but I do not consider their prices "reasonable" per se.