Toontown and Fantasyland at DL are both so much bigger than WDW. They have many more attractions that you will want to see. Pirates at DL is much longer and way better than WDW. There is an entire story to DL POTC, while WDW just puts you in the middle of the pirates fighting the town.
Do not miss Aladdin. I hope it will be playing again when you arrive. It was dark when we went in mid-Sept, but we saw it in June and loved it. Fantastic show. You'll want to do Fantasmic at DL because the show is much better - no Pocohontas stuff (thank God), they have Peter Pan instead and makes much more sense.
The Paradise Pier area of Cal Adv is neat at night. Teenagers will enjoy this part of Cal Adv. And once they see it, they may want to do an extra day here.
You can probably do it in two days, but you will either miss lots of things if the lines are long or you will be rushing around. DL hours are not as long as WDW, either. They open later in the AM and Cal Adv often closes earlier in the evening. Check the website to see what hours they will have when you go.