All the above are great ideas.
If you wanted a day trip I can recommend the following:
Puerto Galera, if you leave early enough, could get you back the next day.
I have heard it called a less crowded and expensive Boracay.
I think the swimming is not quite as nice, but the diving and snorkeling is better.
Angeles city can be fun.
Other than the usual reasons people go there, there is a small American cemetery dating back to WWI that is worth a visit.
There is also a small museum covering the Clark airfield era.
If you take the SETEX route, it is a short trip.
Baguio city is worth a visit.
Most people take the overnight bus and get there in the morning.
As I did not sleep so well on the bus, I napped for a few hours.
Baugio is slightly cooler than the rest of the Philippines, although it did not seem that different to me.
You can see Camp John Hay and several reminders of the Americans who designed the city. The lake in the middle of the square is nice to see.
Much of the city still used American 120v last time I was there, although I have heard that is changing.
Lastly, I might look into Subic.
You can see what is left of the American Navy base located there.
I found it amusing to note that the manhole covers were transported there from Wisconsin.
There are many resorts and restaurants along the beach, as well as a museum depicting life on a navy base.