If your father does not actively disable the caller ID blocking when he dials your number (*82 on most systems) then his call will be rejected and sent to voice mail by DND. Your phone can't let it through because it has no idea who the caller is. As amy_lou pointed out, if they call back again within 3 minutes (and you have repeated calls turned on, the second call should be allowed through... but that assumes that caller ID identifies the caller and the phone knows it's the second time they've called. You'll have to test it with his caller ID blocked to see if it behaves the same way under those circumstances. Personally, I would hope it would continue to block it... but that's just me.
The BEST solution is make sure that he dials *82 before your phone number so that you know it's him. He can just program that into the dialing string on his phone(s) if it's too much work to dial it by hand...