Hello from Okinawa to Russia!

How long will you be staying? It may be difficult to find a room in that price range in August on Okinawa Island. Most hotels in Japan also charge per person, which makes things expensive. There are, of course cheaper hotels, but you will be a little further away from the beach...There may also be a communication problem if you do not speak Japanese when staying at a smaller hotel and there is little information available on the internet in English..etc. Here are a few of the popular resorts on the beach:

http://www.alivila.co.jp/en/

http://anamanza.co.jp/

www.daiwaresort.co.jp/english/28_okina.html

http://www.moonbeach.co.jp/

For cheaper accommodations close to a stunning beach, I would suggest that you try and go to one of the smaller islands...Tokashiki Island is very beautiful and is about an hour away from Naha by ferry. The island has a nice, little beach town called Aharen with many small hotels. Again, most of the information will be in Japanese, but here is a simple website in English:

http://www.vill.tokashiki.okinawa.jp/en/

Here is another English link to some cabins in Tokashiki Island. This may not be what you are looking for, but it may be economical for a family, or you can try emailing the couple that takes care of these cabins and ask them for advice on a hotel closer to the beach:

www.tokashiki-guesthouse.com/en/rates.htm

Another really beautiful island further south of the main island is Ishigaki. There is more to do here than on Tokashiki Island, but it is further away, accessible by overnight ferry. The good think about Ishigaki is that there is more English information, including a tour company that may be able to help you set up your trip in English:

www.hirata-group.co.jp/english/index.jsp

Good Luck!

Kenny

$300-350 for total or one night expense?

if it is for a night, you can find it.

But during 10-17th Aug, must be too expensive more than twice as another season.

If you drive a car in Okinawa, you can find nice one beside beach. If you don't and if must find around Naha city, barely find beside beach.