Hi Crystal,
Thanks so much for your question. It sounds like you have some yummy dining plans coming up!
The easiest way to get from Disney's Hollywood Studios to
'Ohana is to take a bus to Disney's Polynesian Village Resort, where the restaurant is located, when you exit the park.
I would allow 60-90 minutes for travel in case you have to wait for a bus or any other unforeseen circumstances. I always prefer to err on the early side when I have reservations.
Another option that may save you some time is to take a taxi. Of course, this would have an added cost so I always try to take advantage of the complimentary Resort transportation when time allows.
Please let us know if you have any other questions as you plan your time at Walt Disney World Resort, Crystal.
Aloha!
Andrea U.