Not sure you should opt for Sai Kung etc without a real good first look. If that is the life style you want - village housing - you might love it but...on weekends getting in there is tough as it getting out at the end of the day. I guess if you live there it is not so much an issue for you.
High rise is HK most places other than out there.
Sai Wan Ho has some very good developments and Taikoo/Quarry Bay would meet your budget as you likely want to central to work, shopping, etc and places to go with your young child.
I set a lower budget with my wife in Canada but liked Taikoo near Jusco for food shopping.