I was a flight attendant for 22 years and had to "retire" early because of my weight. I wish I could say you will be treated courteously by the airlines - but I doubt it. I would call your airline and ask to speak to a supervisor. I would explain my dilema and ask for their advice. I know that, insofar as seat belts, you can ask for two extensions which should help. But the seats are NARROW and the bathrooms are SMALL. If you can take a night flight it might help. Maybe the flight wouldn't be crowded and you could use two seats. And, if you find a nice flight attendant (The weight restrictions have been declared illegal so you might find an "overweight" flight attendant) she/he might help you with the bathroom situation by blocking the door open for you and providing privacy. The airlines definitely do not cater to people who are not thin. Even when I was 5'4" and 140 pounds I had a problem fitting in the coach seats. Good luck! Make up your mind you ARE going to Hawaii. If you have never been it's well worth the effort!!!!