In France (where I am from), there is this social rule that you only give gifts to people who invited you to the celebration (birthday, christening, marriage, etc...) or gave you a gift linked to said celebration. So, basically, gift-giving is for reciprocating something. It's a way to thank someone for spending money or time on you.
Furthermore, the value of the gift needs to be related to how much the person spends on you. So, if someone helped you with a small favor, you can reciprocate by giving them a small gift, but it would be considered bad etiquette/rude to give them something of too much value (because then, they will be the one feeling like they have an obligation toward you).
I don't know what the culture is in Indonesia, but if it's similar to France and taking into account that your friends have "said they'll give a party at a later time", here is what I would do:
When the topic of the wedding is brought up, casually asked your friend if they know when they will be doing their wedding party. Then say something like:
I can't wait to have the party so that I can finally give you your gifts!
By doing that, your friends will be reassured that you are still planning to give them a gift and that you are simply waiting for the party to do so.
If it turns out your friends won't do a party after all, then according to the (French) social etiquette, you can still give them a small gift. You just need to make sure that it's noticeably smaller than if there had been a party.
