i would look along sai sha road. there are buses going both ways: to sai kung and to ma on shan/shatin. also, taxis are plentiful.
otherwise, you could look at sha kok mei. it's only a 5-10 minute walk to sai kung town, well populated, many expats...you'd at least be able to get 700'... if your budget is around $20k, then i would go to one of the agents and ask them to show you anything and everything within your budget, you may be lucky and even get a 1400' duplex.... then compare.
we live out in the country park and it has public transport, but it's not great(the transport, not the park... we enjoy the park very much!). when we had our helper, though, she was always home before 10pm because the last bus was 9:30. her husband stays out until around midnight and shares a taxi home with some of the other male helpers in the area.
there are lots of activities in sai kung town as well as a great local kindergarten and a good local primary school. (this may not apply to you though, as you may get subsidised schooling for your little ones). there are ballet classes, pottery, mandarin, swimming, tennis, etc all right in town.
could also look at po lo che village.
the ONLY village that i've ever heard of with triad issues is nam wai (closer to the large round-about going up towards clearwater bay).
security? we have dogs, so we've never had a problem... but even when i lived in a village years ago, we never had any problem... just don't keep loads of cash lying around. and make sure to lock up any valuables. if you're very worried, buy a safe for your cupboard to put all important documents, jewellry etc.
if you have any specific questions, please do not hesitate to ask. personally, i would not want to go back to living in a high rise... but that's me and village life doesn't suit everyone.