A couple of thoughts I've had which haven't been raised yet.
1. I'm not sure that working from home is going to be viable with 4 (and a 5th coming) kids running around. It might work in your typical large American home, but here in HK? I'm not so sure. Sounds travel easily through the thin walls here and there's bound to be a lot of disturbance and distractions throughout the day.
2. You'll want to build up a much better picture of your potential monthly expenses before committing to the move. Even sticking with the local school system, it can get expensive. Uniforms, schools buses, books, all of these x4 (And later x5). How about food? Feeding a large family used to a western diet is not going to be cheap unless you can adapt to a more local diet. How about going back home once in a while? Trips for 6 back to the US aren't going to be cheap either. All these need to be budgeted for and much more besides. I'm guessing that without keeping a tight control on your expenses you could be looking at spending easily over 100K / month.