Welcome... you will get some good advice from the forum members here.
If i was you i would take a small gift (pasalubong) for your partners mum and dad and maybe something for any kids in the family. Doesn't have to be expensive

In Philippine culture you are kind of expected to bring gifts when you have traveled from somewhere else. Even though some people may disagree with this i personally think it is quite appropriate to bring a gift. If you went to your friends in the UK for dinner you would probably take a bottle of wine. Same thing.

What gifts? The first time it can be a bit tricky as you haven't met them in person. Something from the UK would go down well. Might only be a t-shirt but as long as it says Great Britain or England it would be unique.
For the kids CHOCOLATE always goes down well. You can buy them at the duty free shop in the airport when you land. Saves all the hassle of bringing them from the UK.

Credit/debit cards are a lot more widely accepted than they used to be. You can use your UK cards to withdraw money at any ATM machine. I'm not sure of the charges but if you search the forum someone will have already written about this. Have read some members have had there's blocked when trying to use them here. Make sure you inform the bank before you go!

As other members have already said dont get carried away with your spending.