Zaheer

Just being around Sora puts the two of them in the line of fire of some of the most powerful beings in the Kingdom Hearts universe. Hell, the last boss of KH1 was against a giant living battleship

Mickey is arguably more powerful than either Sora or Riku due to the benefit of having 10+ years of experience as a Keyblade wielder; he was there at the rise of Xehonart’s scheme and watched three of his friends all suffer horrible fates. 

Mickey knows how dangerous this is

Since then most of Mickey’s actions have been behind the scenes, working in the shadows while all the attention is focused squarely on Sora. Mickey could have just brought his two best friends with him, but he trusts them to be on the front lines with Sora because he knows the two of them will be alright

Even Yen Sid who’s more powerful than any of them knows Sora needs Donald and Goofy at his side for what’s to come in Kingdom Hearts 3

And what DO they bring to the team?

Goofy despite being…Goofy, is surprisingly insightful and quick on the uptake. He’s constantly shown to pick up on things Sora and Donald overlook (Like how he saw straight through Mulan’s disguise, or how he knew Pluto would lead them to the Keyblade even though Donald disagreed) and of course the fact that he took a rock to the head to save Mickey. Also, he was the first to defect back to Sora and disobey Mickey’s orders to save him from Riku

Donald meanwhile was responsible for the group being able to blend in in Halloween Town, and he is the one who transformed them to survive in Atlantica in KH1. Despite being at odds with Sora from time to time and initially only seeing him as a means to an end, he too disobeyed Mickey to go back to him.

They jumped into the journal world to help Data-Sora, they saved Sora from being killed by Larxene when he had abandoned them, they disobeyed Mickey a second time to help Sora defend Radiant Garden from the Heartless, and even if it was mostly an accident they saved Mickey and Riku from the Xehonart squad in Dream Drop Distance.

Also worth noting: Sora is seriously depressed. He hides it but it occasionally shows that he’s not okay. As cheesy as “My friends are my power!” is, Sora wouldn’t be where he is now without the two of them, physically and emotionally.

Donald and Goofy deserve way more credit, and I hope in KH3 they’ll continue to be what they’ve always been, and I hope that they have a part to play in the final battle

I solemnly swear that I am up to no good.