This is a really difficult for anyone answer but yourself

I too haven't seen my Father since I was 3 or 4 years old and I have no desire to. My Mum re-married and my stepdad is my Dad and Father to me, always has been and always will.

It sounds like your Dad might have realised that he made a mistake, we're all capable of making them. If you feel that there is a chance of patching things up now might be a good opportunity to start the ball rolling.

I would open the cards if you feel that way and see what he's written inside and not what (or how much) he's put in there. Whether you then accept that is down to you.

If there is no hope for patching things up I think I'd return them unopened with a note explaining how you feel, this might also make him realise how he's hurt you.

Sorry I don't have the definitive answer but it's just some suggestions.