Japan is generally a great place to travel with kids: it's safe, clean, full of mod cons and easy to get around. Not many sights go out of their way to appeal to children, so you may have to get creative, but teens should be easily wowed by pop culture and dazzling cityscapes.
Pop culture galore: stay in a hotel with a giant Godzilla statue, explore the world of Japan's top animator, Miyazaki Hayao, at the Ghibli Museum or shop for character goods. Teens will love neighbourhoods like Harajuku and Shibuya.
Meet the deer of Nara-kōen, see the castle in Himeji and bask in the colourful lights of Osaka.
Hiking and skiing in the Alps, cycling past rice fields and exploring old farm villages outside Takayama and a fantastic castle in Matsumoto.
Great skiing, snowboarding, hiking and camping opportunities for outdoorsy families.
Work in a little beach time in subtropical Okinawa – a popular destination for local families. Off-the-beaten-track island Taketomi is great for kids: there are no cars (only bicycles!) and great, low-key beaches.
Larger cities have more public facilities for nappy-changing and nursing; department stores, shopping malls and larger train stations are all good bets. Breastfeeding is generally not done in public, though some mums do (find a quiet corner and use a shawl).
Local families take a lot of meals at 'family restaurants' (ファミレス; famiresu). Chains like Gusto, Jonathan's, Saizeriya and Royal Host have kids' meals, high chairs, big booths and nonsmoking sections. High chairs are not as common as in the West. Supermarkets, bakeries, fast-food restaurants and convenience stores stock sandwiches and other foods that kids are likely to go for; supermarkets carry baby food.
If your child has allergies, get someone (perhaps at your accommodation) to write them down in Japanese. Chain restaurants often have common allergens marked on the menus with icons. If you plan to stay at a ryokan with a meal plan, discuss any menu modifications when you book (places that regularly get foreign tourists should be accommodating); you can also book a stay without meals.
Tokyo Disney Resort, Tokyo Visit the only-in-Japan Disney Sea park (along with classic Disney attractions).
Universal Studios Japan, Osaka The Japanese version of the American cinema theme park.
Tokyo Dome City, Tokyo Kiddie rides and a roller coaster among Tokyo's skyscrapers.
Sky Circus, Tokyo Experience being virtually shot out of a cannon over Tokyo.
Fuji-Q Highland, Fuji-Yoshida Best known for its thrill rides.
Japanese kids love trains; odds are yours will, too. Just getting to ride the shinkansen is a neat experience.
All of the following have child-sized bikes, though urban tours are better for older kids.
Baseball is Japan's most popular sport and the crowds go wild for it, really putting on a show. This can be a really fun experience for kids, even if they're not already fans of the sport. All major cities have a local team. The season is March to October.
Every Japanese city has a karaoke parlour with English-language song catalogues listing all the latest hits (and plenty of classics too). A great way to spend a rainy afternoon.
Very little special planning is necessary for travellers with children heading to Japan.
Most hotels can provide a cot for an extra fee (providing there's enough room for one). Some hotels have triple rooms, but quads or rooms with two queen-sized beds are rare, as are conjoining rooms.
Local families often stay in traditional accommodation (ryokan and minshuku) with large tatami rooms that can hold up to four or five futons, laid out in a row. Unfortunately this can be pricey: if your child is old enough to require their own futon, the price is often the same or near to that of an adult (minus a discount for meals).
Hostels and guesthouses often have family rooms (or at worst, a four-person dorm room that you can book out); again there is usually no discounted child price. These also often have handy kitchen facilities.
Do bring any medicines that your child takes regularly (or may need), as Japanese pharmacies don't sell foreign medications (though similar ones can be found). The shinkansen (bullet train) is very smooth and few travellers report feeling motion sickness, but if your child is very sensitive, you might consider preventative measures; winding mountain roads are as nausea-inducing as anywhere.
Pharmacies stock nappies (diapers) and wipes; grocery stores and pharmacies carry baby food. You can find some common foreign snack foods (like certain brands of cookies) in grocery stores and convenience stores, but the selection is not huge. You might want to pack small plastic forks and spoons, as not all restaurants have these on hand.