You will find in 3rd world countries the kid that learns English in the family is usually the one that achieves and succeeds. I have seen this where the one kid out of the family of say 5 learns English and the others are left behind.

The language of the country they live in.

English, English and more English. If they choose to live in Mexico, they need to learn Spanish. China, Chinese. You get the idea. This is the United States, we speak English.

If I were a parent, I'd choose English because my kids would have better work prospects when they grow up if they learn English early on.

I think that the parents would be the best judge of what would be most useful for the children based on what they use the most in their day to day lives. Teaching as much as possible as quickly as possible is the best course, because the children are most able to learn multiple languages at younger ages. Personally, I think that the world shrinking every year adds value to English as a secondary language.

I would go Bahasa, Portuguese and English.

I'm just going to base this answer on the information that you have provided and the fact it was presented in English.
English.
No-one on the planet really suffers from knowing English, I would argue the opposite in fact. Merchants who try to sell their wares to tourists learn as much English as necessary to help them sell enough to make a living. This is true even when trading among other merchants when they both speak different languages. Language, much like reading and writing, is a skill. English can be found almost anywhere, Turkey, China, Japan, Mexico, United States, Australia, Iraq, Italy... I'm pretty sure you can find it in most of Europe, India, Canada, Russia, and just about everywhere. But I only listed places that I have had first hand experiences with.
If for cultural reasons everyone wants to hold onto their native language then I encourage learning it. Even if the only people who would be able to communicate are close family members. But for practical reasons that could be tied to future success, learn the lingua franca of the planet. The Language that bridges trade, education and politics.

For a school, your goal at a young age is to ensure the kids are able to become part of society, so the languages that are most important are the ones that they'll use the most often with a need to be fluent in such.

This means Tatum will come first, as it's actually used the most by the people around them. The "official" language doesn't matter much - Canada's "official sport" is lacrosse, not hockey, as an example of whether something being official or not means anything in terms of actual practical value. If Portuguese isn't used on a regular basis, then it seriously doesn't matter if it's the official language or not. If it's used commonly in cities or something, then yes, they should definitely have that next on the list of things to learn. If this is a series of small, remote villages, where they're probably never going to leave their villages, then Bahasa may be of more use to them. If you want them to be able to prosper by being able to leave the village and interact with the wider world, then English is the international language of commerce, aeronautics and science, so that would be a huge boost to their ability to bring prosperity to their home region. Mandarin's another really big one which is almost as important as English, and may be more important depending on the specific region.

But yeah, basically it comes down to an order of "which will you use the most often and actually need to know on a regular basis in order to prosper" as it were - so probably Tatum first and foremost. Everything else is going to be weighted upon frequency of use and the kind of use.

I've always been leery of saying this because I don't want anyone to think I'm a nationalist or any kind of bigot but... English has become the international language of business. Knowing how to communicate in English is an immediate advantage for personal success simply because it has become the most widely spoken language.

In America, English of course.

In the case of Timor Leste, if there is a national language and different dialects, they should all be taught.

English, Russian, Chinese and French.

Every major business language used.

I personally feel that they should be taught the language of the country/region in which they live... there is ALWAYS one "main" language

For example we are in America and speak English... yes, we have other languages here, but people come HERE... so speak the "native" language of HERE

Complicated. Research suggests teaching kids multiple languages early makes 'em smarter--makes changes to the way the brain functions/organizes itself. English would be sensible if you have an eye toward competing globally in the future (or maybe Mandarin Chinese). But, there's a real communication problem locally, it sounds like. I'm not sure it makes a lot of sense for people here in the western world to influence the choice. The choice will emerge from a convergence of their own values and individual needs. I know that's not much of an answer, but I'm not sure I'd be able to consider all of the possible impacts of the decision. I don't know anything about Timor Leste. I suck in geography. Is that in the southern part of Texas?

English

The language that a child requires to function in the area of socierty they are in. Based on what you have written (I know very little about the education in the area) I would say Tatum and Portuguese (as these are the most common and official languages) As the world becomes "smaller" and more people speak English maybe that could be incorperated into the lessons especially for the children who show an interest. This is only my opinion.