If they were planning a move to Hawaii for several years, would they have gotten passports not knowing it would become a state in 1959?
I don’t think a passport is required for a territory any more than it would be for a state.
A passport would have been necessary for travel to Hawaii (and passage home) only if they had planned their trip to Hawaii before the American annexation in 1898 [or possibly to those far northwestern islands under Japanese occupation in 1942]. And then only if passport rules were similar then to what they are now.
According to the family story, they moved to Hawaii in 1960.