1.) Kowloon is part of Hong Kong.
2.) Kowloon and Kowloon Tong aren't very desirable areas. They are known to be areas with low income people or people on government support.
3.) You may not want to limit yourself to Kowloon. Hong Kong is very small and public transportation is very advanced (you will remember my words once you see it). Even if you live in Kowloon Tong, you may want to explore other areas and districts, such as those on the island, which is only few minutes away by subway.
4.) Why would you want to limit your social circles to Americans only? Here you have the opportunity of a lifetime - to meet people of diverse backgrounds and enrich your own life. Why throw that chance away? Make your children learn Cantonese and especially Mandarin. Don't be afraid to enroll them into local schools with local kids. One day they will thank you (and they may become so rich as a result of that, they may not put you in a nursing home).
5.) According to the US consulate, there are about 50,000 Americans in HK, but that number is very likley much higher, as many Americans refuse to register with the US consulate. Keep the big brother out of our lives!
6.) Congratulation on this wonderful opportunity. You are very lucky !!!!!!!!!!!