If you can get a position at a decent international school, you will get a good salary, a housing allowance, a nice end of contract bonus and free or subsidized tuition in a great school for your kids so it is absolutely worth it to move. If you fit in well, your husband would stand a great chance to find employment at the school and/or in a rugby related position and could also make lots of money tutoring kids from your school.
Apart from housing which will not be the same as in New Zealand, your cost of living can be lower particularly if you don't get a car which is easy to do in HK. The taxes are obviously much lower and the salary in a good international school is almost double the gross you make in NZ. Nice houses are not cheap in NZ these days particularly major cities so coming to HK for a few years will allow you to either clear your mortgage or buy a nice home if you decide to go back. At some of the schools, you get a 20-25% bonus at the end of your contract. Even if you spend everything, you can easily leave with 50 000 NZ after two years. If you manage to teach in an IB school, you will also get your certification which will make getting well paid jobs anywhere in the world fairly easy.