Didn't know the bus 52 / 55 thing was changed. Too bad since, if you want to do the circle island just for the views but not stop, you have to stop in Haleiwa to switch buses. If I read the maps right, both go all the way through the main area of Haleiwa so it isn't too bad.

Maortega, I'm not a big coffee drinker, but my friends who are always look forward to me coming back to the mainland to visit and bring Kona coffee. At restaurants (or stores to buy packages of it) be aware that they'll often have "Kona coffee" in big letters, but it is often only 10% Kona. The 100% Kona is considerably more costly. There are other Hawaiian coffees and some may prefer them on personal taste. I know there is Waialua coffee (town right next to Haleiwa). And Molokai coffee. Probably others.

If you are driving near Dole Plantation, there is a place right near there that carries an number of different kinds with samples as I recall. Don't recall the name of the place, but easy to get to. If driving back to Honolulu from Dole Plantation, just turn right at the first traffic light. The building is immediately on your left after making the turn. They have other stuff too, like shave ice, but I never tried their version.

Can't really tell you much about souvenirs since so much of that would be personal taste. You'll find coconuts you can literally mail without packing. Usually with colorful designs on them, but I would suspect they could get scratched up pretty good when shipping that way. Really, best approach is just to go places where they sell lots of souvenir stuff and see what options there are. That's one reason the Aloha stadium Swap Meet is a good place. Lots of tent type booths all around the outside of the stadium - sometimes more than one row deep. Lots of duplication, but I have found unique stuff too. Duke's Lane in Waikiki is sort of a much tinier version of it. Never compared the prices though. I have noted that shirts often have the collar tag cut which, I think, is a sign that it is "factory seconds". So should be a flaw in them someplace, but you can examine before buying and I never found anything wrong with any I bought. Only obvious flaw in anything I even saw at the swap meet was a beach towel that spelled one of the islands wrong.