I have booked Airasia tickets since early this year for us to go Krabi in January 2013 and it only cost us RM1000 for the 7 of us with return tickets, hot seats and sufficient baggages!
Anyway, I came across these villas in Bali and Krabi. I think it is good for a family holiday. You have a kitchen for cooking and your private own pools, and if you feel posh enough, you could get the chef to cook for you too! Also, own Tuk Tuk service and transfers from and to Airport, the transportation is already worth a bit of saving. Kids can play around instead of stuck in a confine space of a hotel room and you can be more relax with your time table, like cooking on your own and if the kids are tired, they can take a nap or go anywhere you like with the in house Tuk Tuk service.
Villas in Krabi, Thailand
Villas in Bali (the are more villas website in Bali, you can google for them like Seminyak villa and etc).