Apple Push Notification feature as a mandatory feature of app

We're creating some app for iOS devices and we would like to use Apple Push Notifications as one of mandatory features of our app (actually without push notifications our app will be useless). But actually Apple's manual said that push notifications is an optional feature and nobody can guarantee the delivery of the notifications. It's Ok if we just warn user about that and tell him to switch this option on in device settings and that he should be online to use our app, but we're worrying that Apple could reject our app if we require user to approve push notifications.

Has anybody some experience about that? Thanks in advance