Translation:Kaʻiulani is going to go to practice.
Yes, e-painu-ana can mark future tense, but it can also mark uncompleted or ongoing action (compared to ua-painu which marks completed action) in the past or present. p 116 of this online resource has an explanation and examples. https://hawaiian-grammar.org/wp-content/uploads/2020/01/Hawaiian-Reference-Grammar-V1-Jan2020-1.pdf
Yours could be correct depending on context of the situation being spoken about and the context of the translator. For translators who translate word-for-word, and who are using a source book that maps "will" one-to-one onto e-verb, your translation will sound wrong. This is often true of beginning students, because their teachers mark them wrong for not using word-specific translations. Other translators will map a situation (rather than specific words) onto a particular tense. For example, as a native speaker of American English, I sometimes say "will" meaning simple future tense. In that case e-verb-ana would work. But if I say "will" with a " should" feeling (e.g. yes Ka'iulani WILL go to practice), then it would be better translated as e-verb. Check out p. 117 of this source for a detailed explanation of e-verb meanings: https://hawaiian-grammar.org/wp-content/uploads/2020/01/Hawaiian-Reference-Grammar-V1-Jan2020-1.pdf