I was so engrossed in the USA part that I failed to notice the above. OK, 2 weeks is a long time for Tokyo or Hong Kong. They are both fun/enjoyable cities but neither has 2 weeks worth of sightseeing. You are probably stuck with 2 weeks in HK, which is probably the more fun place if you are English speaking anyway.
HK is more convenient for English speakers, yes, but not a better city to visit. There's just not much there. I already listed a few places in the other thread, but HK and shopping go hand-in-hand. You can do things like:
- the new Disney (would be interesting to see a Chinese Disney, I guess), and the rest of Lan Tau island.
- Ocean Park
- Victoria Peak (walk it, don't tram it.....I used to do it in the morning with my cousin's dog)
- the light show at the harbour between the harbour on Hong Kong Island, and Kowloon). There's a light show every night, and Hong Kong has the best city skyline in the world, IMO.
- and maybe take a tour of the New Territories.
- Shop. Shop in Tsim Sha Tsui (TST), or anywhere in Kowloon, for that matter. Go to Central on Hong Kong Island and window-shop.

I like HK Island better, as I'm more familiar with it, but meh.
You need 5 days. That's it. Anymore time than that, and you really are wasting your time. If you're stuck in HK for 2 weeks, you may as well take the train to China (which requires a separate Tourist Visa, I think), maybe Guangdong/Guangzhou, and even Shanghai or something. Whatever. You have so much time. Or how about a quick visit to Taiwan.
In Tokyo, there's just so much stuff for a tourist to do. It's not as easy to get around, but whatever. You can also travel 45 - 60 minutes to Kamakura to see the big Buddha statue there. That area also has a beach, so if you're keen, go for a swim.

If you're done with Tokyo, go to Fujinomiya (where you'd go to start your climb to the top of Mt. Fuji). If you're done there, go to Kyoto. Then go to Nara. Get a 7 day Japan Rail Pass, and you can just go from Tokyo to Hiroshima. It takes around 7 total hours by Shinkansen.

I did it. I had to get to a Christmas party in Tokyo with around 14 friends I hadn't seen in around 2 or 3 years.
And why oh why would you go to the North Island in New Zealand for 2 weeks.
1. You picked the wrong island to take such a road trip.
2. Change your plans.

3. Change your plans, but maybe add a short 3 day trip to Melbourne as well. The Little Penguins are an incredible sight to see. Just the cutest little things ever.