Check out Apo Island (Paul's Diving)
It's worth at least a few days. Not much to do surface side - a little bit of hiking maybe some snorkeling. I spent 5 days just diving and really liked diving the same locations a couple of times. The currents really changed each day and the you will always see something new for sea life and nice corals. It only takes a 15 minute boat ride to get to any of the dive sites and you come back to the lodge afterwards. Inexpensive accomodation and friendly staff. A nice little adventure getting there too.
Malapascua Island
(Thresher Sharker Divers)
http://www.malapascua-diving.com/index.html
A variety of dive sites - walls, wrecks and fish. Inexpensive accomodations or pricier if you prefer. Nice assortment of restaurants to choose from. Half a dozen dive shops to pick from although I would highly recommend Thresher Shark Divers - smaller operation, more individual attention and friendly staff. Andrea and Treavor used to work at Bubbles07 and finally set up their own operation. I have dived with them on three trips so far and plan to again. It takes about 2.5 hours to walk around the whole island which is relatively flat but you can take in the town's local basketball games in the afternoon.
Coron - on Basuanga Island (Northern Palawan Province)
Great WW2 wreck diving. Mostly Japanese freighters which were salvaged by the US after recapturing the islands so they are busted wide open with lots of life on them. The deepest is at about 120 feet on the bottom. Little bit bigger town than the other locations but not much to do. More vertical hiking adventure available though.
These three places don't offer a whole lot for the non-diver. Just depends on how much stimilation your friend needs to keep occupied beyond reading, sunning and swimming.
Have fun. I'm going May 19th and will be visiting Ilo Ilo and then back to Malapascua for some great diving.
Jason