Is there a way to disable incoming calls without using airplane mode?

Sure, just use the do not disturb feature, its under settings

Why don't you just turn Airplane mode on and then turn WiFi back on in settings?

I want to play my itunes music playlist for an event, but I don't want any calls or mail / text notifications during this time.

Is there a way to do that?

Just to be clear, dnd does actually only silence calls and notifications, according to support article ht5463

http://support.apple.com/kb/HT5463

You can use the Do Not Disturb setting while your iOS device is locked to silence calls, alerts, and notifications.

DND does not prevent calls and texts.

Use the privacy settings in DND to stop all calls coming through

also under settings, go to general, and you can turn off cellular data. For the text issue, I'd try going to settings, imessage, and turn everything off in there

Or you could go to settings/notifications/Do not disturb and then who you want to allow/disallow calls from and for how long

edited for wrong info

cellular data only controls internet usage over cell networks, not voice calls