The subtropical climate of Hong Kong means that summers are particularly hot and wet, and spring is warm and humid. November is the sweet spot, with clear, sunny days and mild temperatures. During your trip, you'll want to take a traditional junk boat ride on the harbour (seen here) and check out the sweeping city views from Victoria Peak, which you can reach by tram. Another can't miss? Stockton, a hidden speakeasy-style whiskey bar in Central.
I’m not really an expert on surf destinations and even less so on skate parks, although I am aware of many places that do have good surf beaches. From Ireland I think your two best bets would be either Rincon, Puerto Rico, which has the best surfing in the Caribbean and is good for longer rentals like that. You could get a reasonably priced flight into San Juan, which is also a really nice place with some surfing and great beaches, and then hire a car for the drive to Rincon.
The rainy season is over so it's an ideal time to base yourself in Chiang Mai for some outdoor activities in the area. There are temples like crazy in the city center between the old walls, but even more interesting ones in the area just around Chiang Mai. There's also great trekking and such, available quite affordably from any travel agency in the city.
As for Malaysia, I love it there too, but it has very few nice beaches in the main part of the country (not including Borneo). But now that you mention it, they do have some nice beaches in Penang, which is the best tourist area anyway. If you search for hotels in Penang, make sure that they are on or very near a nice beach. Most of the island does not have sandy beaches, but some parts do.
Picking a good time to visit Morocco that suits its two climate zones, the Sahara Desert, the Atlas Mountains, and the coastlines of the Atlantic Ocean is never an easy task. The weather varies wildly according to the season and where you’re planning to explore, but for a great experience at most tourist destinations, the cooler months from October through to April are popular amongst most visitors.
Lovers of historic architecture should consider tiny Malta in November, which still basks in glorious warm weather as much of Europe starts to shiver. The baroque palaces, churches and fortifications of its harbour-hugging capital Valletta look much the same as they did 400 years ago, and are extra lovely when observed from a traditional dghajsa (open boat) water taxi. If a life on the high seas has always appealed, then charter a course for the Cayman Islands come November, when the serene Caribbean isle hosts Pirate Week, a fun-filled festival that includes costume contests, street dancing and a horde of swashbucklers ‘invading’ the island and capturing the governor.
Rio is probably the most beautiful city in the world as far as the setting is concerned, but it’s also famous for petty crime. As you mentioned, I think it’s quite easy to stay safe as long as you are aware of the situation. The biggest problem by far is tourists getting robbed by someone holding a knife or sometimes a gun, and they are often in groups. However, this almost always happens to people who are walking close to the water on the beaches after the crowds have gone for the day. The sidewalks along Copacabana and Ipanema are brightly lit and safe, but there is a mound of sand between the sidewalk and the water, so if you go to the water you can’t be seen by the security guards and police on the street. As long as you avoid that, and any other situation where you are alone in a dark place late at night, you’ll be fine.
Otherwise the big draws are the Great Barrier Reef, which is obviously focused on diving, snorkeling, and water activities, so it may not be too interesting, and Uluru, which is the big rock in the center of the country (and not near anything else of interest). There is also wine regions in the south near Sydney, and of course nature parks to see kangaroos and the other indigenous animals.
In Rome, the Coliseum and Ancient Rome are outdoors, but the city also doesn’t get as cold as the others so most likely you’ll be fine if you bundle up a bit. In Venice, they often have those floods during December, but they come and go every 6 hours so even if you get unlucky you’ll still be able to get around half the day, and it’s a small city anyway.
Far from the crowds and heat of summer, a visitor to Rome in December will find that it’s a lovely time there, with fewer lines at popular tourist spots, more attractive prices, and a chill in the air. With a warm jacket, comfortable shoes, cozy hat and gloves, you’re ready to explore the Eternal City. Stroll through the main streets to enjoy colorful lights, decorated trees, and Nativity scenes. The Piazza Navona hosts a Christmas market, and stores welcome shoppers with longer hours and attractive displays. Rome’s Jewish community celebrates Hanukkah with a large Menorah in Piazza Barberini where candles are lit each evening of the eight-night holiday, this year from December 2–10. The Catholic community celebrates the Immaculate Conception on December 8 when the Pope leads a procession from the Vatican to the Piazza di Spagna. December is the perfect time to visit the Vatican Museum, Sistine Chapel, St. Peter’s Basilica, Colosseum, Trevi Fountain, and museums that are usually filled with tourists during warmer months. Even without crowds, it’s still most convenient to book ahead through a tour company such as City Wonders or Access Italy, for no-wait entry, professional guides, and early admission. Food is always one of the great pleasures of a visit to Italy, and in December, a warming plate of spaghetti carbonara or hot chocolate and seasonal panettone taste especially good. The new Pantheon Iconic Rome Hotel, Autograph Collection is a convenient home base in the center of the action with a beautiful rooftop overlooking the Pantheon.
Two of the easier other choices would be London or Madrid. From Amsterdam you can take a train to Brussels and then change for the Eurostar train to London, or you can fly. From London to Barcelona you’d want to fly for sure. If you chose Madrid you can go to Amsterdam and then fly to Barcelona and then take a train from Barcelona to Madrid in only 2.5 hours.
You mention New Zealand and of course it’s summer there then, so it would be a good choice. However, all of these places will be crowded and near peak hotel rates if they are warm. So I’ll be happy to give you advice if you tell me if you’d rather visit one or more European cities in the cold season, or if you are looking for a warm place like New Zealand where it will be fairly crowded. By the way, the southern European cities such as Rome and Barcelona are lively and enjoyable that time of year, as the Christmas season goes on, and there aren’t too many tourists except for a few that travel to see their families around the holidays. So it can be a good time for southern Europe, as long as you don’t mind wearing a jacket or jumper during the day, and maybe a bit more in the evening. Give me a bit more guidance and I’ll be happy to try to help. -Roger