Elin, 15, says they have a strong support network which is helping greatly.
"We are trying to fundraise and do what we can like garage sales, raffles, car washes. We are going to try and get as much as we can," she said.
"It is pretty hard for us as a brother and sister to raise so much. I am pretty sure we are the only brother and sister who have made the New Zealand team together for surfing.
"But we can do it."
The New Zealand team competing in the under-16 and under-18 divisions in Portugal is dominated by Bay of Plenty surfers, with eight of the 12 selected coming from the region.
The Tawharu siblings, Kehu Butler, Lea Ririnui, Raiha Ensor and Kea Smith are all Western Bay-based, with Jared Gerbert from Ohope and former Mount surfer Kaya Horne now based in Queensland.
The Bay influence is completed with Mount Maunganui College teacher Kahn Butler named as coach while manager Damian Galvin teaches at Tauranga Boys' College.
Surf conditions in Portugal are expected to be challenging.
"It is going to be like quite solid and punchy so surfing waves on the coast here aren't that good practice," Jonas said.
"But we have got the [Matakana] island which is like real powerful and we make lots of trips over to the West Coast where there are more powerful waves to get us better adapted."
Both siblings are looking to make a major impact at the event.
"I am in the under-18s which is like the prime division, real tough, and the level is insane so top 20 would be like a big achievement for me," Jonas said.
"Also top five out of the 12 in the New Zealand team would be awesome."
For Elin, it is her last year in the under-16s so she wants to improve on her two previous showings at the worlds.
"I got 13th the first time I went so it would be quite cool to get a higher placing than 13th," she said.
"That is my goal again this year. I did the best in the New Zealand team so it would be pretty sick to do that again."
This year she won both divisions at the nationals in the under-16s and under-18s and came third in the open women's division, which she says is probably the highlight of her surfing career.