Depending on how old the relatives are, you may not need an interpreter (not a translator, since translators like myself work only with written materials).

Professional interpreters cost money, as noted above. Think triple digits of dollars per day.

If there are younger relatives, they may be willing to practice their English with you. Everyone under the age of about seventy has studied some English in school, but of course, younger people are more likely to remember it.

I suggest bringing photographs of the family back home and any photos of deceased or first-generation immigrant relatives you might have. Be sure to bring a present for the family, perhaps a coffee table book about your part of the country or some product that is unique to your region. If there are teenagers, bring T-shirts from the best-known local college. But bring something.