While I concur with eatchicago that cast iron makes wonderful cookware at bargain prices, not everyone likes it. It's heavy. It has to be seasoned. It can't go in the dishwasher. You can't cook high-acid foods like tomatoes in it. Before investing in a lot of pieces, check with your dad on whether cast iron suits his cooking style.
In fact, that's really a good idea anyway. Most good cooks are pretty individual in their likes and dislikes when it comes to what they cook with. You might want to let your dad pick out his own birthday cookware. I've been given cookware and tools as gifts, and while I always appreciated the thought, the items were never quite what I'd have bought for myself.
And for all that you think his old pots are crap, he may be attached to them and really be hankering for something like a bread machine. Or a really good chef's knife.
Or, for that matter, a fishing reel. If you were buying a present for your mother, I would tell you flat out, no matter how much she likes to cook, pots and pans are a dangerous birthday gift for a woman, and you should consider something more personal, rather than a tool she'll use to make the family dinner. For a man, I don't know.
Finally, I find my cookware bargains, often, at Marshall's and T.J. Maxx. And while I love All-Clad, I'm a huge fan of heavy, cast alumunium nonstick pans as relatively inexpensive alternatives for many kinds of cooking.