Philippines: Off the Beaten Track Exploration (Singapore)

I am planning to organise a trip to Philippines, specifically the province of Palawan. There's Japanese WWII wreck diving in the north palawan island of Busuanga( + a salt water hot spring, island hopping, African safari etc), then going down to El Nido by a 4 hr boat, before going down to centre to see the largest underground river system in the world. Like to proceed down to Honda Bay and then go back to Puerto Princessa for a plane ride on return leg. In Philippines it is better to go between Jan - Jun; which is the amehan or summer. Right now over there is habagat or raining/typhoon season. I'm open to anyone interested or have any ideas where else to go? Perhaps can make this an exploration series to other province of Philippines in next trip.