제 아내는 하와이를 좋아해서 저거기에 갈까 해요.

여기, 저기, 거기.

여기 refers to a place where the speaker is, it is close to 'right here', with 저기 refers to place little bit away from the speaker, where you can direct your finger to. (i.e. over there)

거기 is more of a generic term to avoid repetition of a place mentioned earlier in context. (that place)

This case, Hawaii is mentioned earlier and the pronoun is for shorten repetition. 거기 sounds more natural for my native Korean ears.

비가 올 테니까 집에 있을까 해요.

Being pedantic here. It sounds perfect in prose Korean in written form. In conversation, I haven't heard this ending '~까 해요' for decades.
It is just a trend, but it might sound a bit old fashioned or bookish person (who speaks prose style in everyday conversation)
Seoul people tends to speak '비가 온대니까 집에 있을라고요' which is grammatically incorrect but more common.

이사할까 했는데 새 직업을 가까이간신히 구했어요.