OK, here is my guidance - take where your husband's work place is and work backwards. For example if he is working in Kowloon, then there is not much point living on south side of HK as the commute will be crazy with two tunnels to commute through.
You want balcony - ok lots of apartments will have this. If you want roof top terrace, then more limited. If you want garden then even more limited. Pool and club facilities - you will need to go with a larger development, a newer one or one where there are more expats - or simply join a club.
Size of flat - assuming your husband's kids will visit, think you should get something at least 1000 sq ft as this will be more comfortable with 3 bedrooms - one for you, one for the kids and one for a study. 1000 sq foot will give good space. Anything smaller and you will feel claustrophobic. Go further out for cheaper flat, go closer you sacrifice size, all else equal.
Cost of rental - I would factor in something like 30%-40% of salary for rent - if you're at the lower end of salary scale ($<$60k/mth) then use higher end of percentage scale, and for higher end of salary scale (>$100k/mth) then use the lower end of percentage scale.