I lived on Lamma for 7 years and was a TESOL teacher also many years ago. These days, I advise parents on placing their children in schools, so with all these hats on, my comments:
- Lamma is fun, not too expensive and great for making friends...as long as you can tolerate the commute.
- As a TESOL teacher, you may well be working eves and weekends. It's difficult to balance that with family life.
- In a few years, Lamma will restrict your choice of schools severely. The local North Lamma gov't school is quite good, but otherwise, your 5 year old will be traveling a lot.
I'd opt for the NT, especially if your wife is Cantonese and you'd like your child to be speaking it early on.
All the best!