I can't really give places to look at, but I will say to avoid the south west, western suberbs. Places around Fairfield, liverpool, Yagoona, Yennora, greenacre. These are all places that are in the news constantly for all the drive by shootings recently. I live in the outer south west and it is lovely out here but to far for your needs.

Maybe places around Bella vista, Dural might be a nice area.
I can garuntee (sp) you won't get anything in that price range around bella vista or dural.
I live in Kings Park (nearly kings langley/quakers hill). its a nice area with lots of families around. there are plenty of 3+ bedroom houses in the area and in that price range. We are about 5 - 10mins max to the hospital and about 40mins to the city (Dh goes regularly as do I). There are some nice schools around also. Your DS is around the same age as my DD and I would happily send my kids to the schools here. It's an older area so lots of trees etc also.