Most people who have a loss want you to acknowledge it (in my personal experience and yes I have too much of it unfortunately). You won’t be hurting them more than they are hurting already.
The simplest thing you can do is send a card saying you love them and you just don’t know what to say. It is much better to say you don’t know what to say than to use cliches.
Another thing you could do is send a care package. There are lots of ideas for care packages surrounding grief if you want any suggestions.
Another idea would be to put their daughters name on some jewelry or a handmade quilt or something like that and send it to them.
Another idea is to think of a memory you have of the daughter and put that in a card. It is very important that you continue to acknowledge her.
Another idea is to send money if you have any extra. With loss comes a huge financial burden.
This is all being said without great understanding of the Micronesian culture as they may have specific cultural beliefs that guide them in their grief process.