For my daughters birthday, we gave invites to her entire class, you can't just invite a few unless you know all the phone numbers of who you want to invite.
We did games, pizza, cake, then presents. After presents (i've noticed at any party) people start to drift out the door. So I figure it's a great way to let people know the party is over.
I generally, if we are not doing a meal party, put out pretzels (or like chex mix), chips and dip, a veggie platter, fruit platter, soda, juice and I have coffee made.