The temperature on the beaches in Okinawa may be pretty much the same as Tokyo today, thanks to an unusual warm spell. But even though the temperature is about the same, the sun is not nearly as strong in Tokyo as it would be in Naha.
Okinawa is on the same latitude as Hawaii, while Tokyo is closer to San Francisco. You may not think that is much of a difference (after all, both have a very nice climate), but while the sea and the winds provide a moderating influence in Hawaii, the sun can be extremely hot.
Not everyone has dark skin (a genetic adaption to strong sun), and there are occasional people who are so prone to skin cancer that it can be triggered by a few unprotected hours in the sun. Or a few days at least.
If you plan to take your kids to a tropical destination, you probably do not belong to the second group. Especially since the disposition tends to be genetic. If you plan to, find a different destination.
But you do not have to suffer from a disposition for skin cancer to suffer in the sun. Contrary to what you may think, even people of African or south Indian descent can get sunburned (as opposed to tanned). If you are not used to the sun, take it slowly the first few days, until you have built up some pigmentation as protection. Use plenty of sun lotion, or even better use plenty of sun lotion and stay in the shade. You get sunlight there too, but it is not at all as strong (i. e. dangerous), since it has lost some of its energy by being reflected.
Sun screens actually work by either reflecting or absorbing the rays of the sun before they get to your skin. The white stuff Australian lifeguards smear on themselves is usually zinc oxide or titanium oxide, both of which appear white to the eye. A white surface actually reflects all possible colors, which is why it shines back all colors. A green surface, on the other hand, absorbs all colors but green, which it reflects. This is why white clothes feel cooler in the tropics - and also why black clothes feel cooler, since they radiate more of the sunlight.
It is the ultraviolet rays which are the most dangerous, since they both have higher energy than the other wavelength, and shorter wavelength. One is the reason for the other, and the result is both that the ultraviolet rays penetrate deeper into the skin and make more damage once they get there. The result is the red and itchy, flaking skin, the result of your skin cells dying from being irradiated with the closest you can come to gamma rays in unadultered nature. No wonder people with a disposition for skin cancer feel afraid. As they should be.
If you have fair skin, you need to be careful. You may not need to be as careful as people in Japan and Korea, where especially old ladies carry parasols to cut out the rays of the sun.
Not protecting yourself from the sun can be dangerous, and it will certainly be painful. One of my own most painful vacation memories was the day after I figured half an hour in the Hawaiian sun on Waikiki beach could not hurt. Just let me tell you it did.
That is not an experience you want your children to have (it will put them off going to Hawaii forever, which is a shame). And it is easily avoided if you dress them in bathing suites that cover at least the upper body, and a cap that covers the neck, nose, and top of the ears.
It is not hard to find full body covering bathing suits for your kids, but you have to look at the label to make sure the cloth cuts out ultraviolet light. That limits the selection a bit, but not that much. And while your kids are small enough, you can still overrule them when it comes to the model (try doing that with a teenager). Go for safety over fashion, they will thank you later (although perhaps not when you show the pictures at the wedding).
But protective swimsuits and a hat is not enough. That cap will come off your childs head at the first opportunity (if you do not have a bucket, it is perfect to carry water that you can pour on your sisters sandcastles). So you need sun tan lotion as well. On any exposed fleck of skin on their bodies. As I mentioned, do not forget the top of the ears and the nose. Use a strong sun protection factor. And it had better be water resistant, if you are going to the beach. The sun lotion will wash off when your kids have a shower in the evening, something they will need since they will be both sweaty and sandy anyway.
Putting on the sunscreen can be a chore and unless you like to endure protests from your children, use a sun tan lotion that is combined with insect repellent.
It may sound weird to talk about insect repellent and mosquito bites at the beach, but if you think about it, thousands of half-naked bodies being baked slowly in the sun must be more attractive to anyone interested in sucking blood than a herd of wildebeest is to a pride of lions. If it was not for spraying with insecticide, beaches would be festering with infections and disease. This was actually the case until the 19th century, when draining the swamps that used to lie behind all beaches (except those in the desert) reduced the rampaging malaria epidemic that also struck many countries in Europe, as far north as Sweden.
Since beaches are (or at least used to be) such hotspots for disease, you want to make sure your kids do not get infected by an insectbite. I wrote in a previous post about how you can protect yourself and your kids from infection. Your children will squirm and squeak when you put on the sun tan lotion, so it makes no sense to try again with the insect repellent.
And do not try to mix them yourself. You will end up with one diluting the other, and anyway none on them will have the effect you expected. Buy a pre-mixed solution, and check that it is approved for children in the agegroup your children are. There are some sunscreens you should not put on children below three because it might irritate the skin or create allergies, and an allergy a child acquires at a very young age will stick around for the rest of their lives. You do not want your kids to have that hanging over them.
I am Wisterian Watertree, recently moved from Tokyo to Sendai, previously of Bangkong and Honolulu. I write about travel, especially with our three beautiful kids (two girls and one boy, soon turning seven - yes. they are triplets). Travel is education and fun rolled into one, and if you are like me, that is something you want to give to your kids. If you want more tips and want to find out when I will publish something, get it from my email list. If you want to be personal, drop me a note on firstname.lastname@example.org, or if you want general tips, follow me on Twitter @wisterianw.