I'd go with the computer desks. Good computer desks nowadays can also be used for study. Desks are something of a long term expenditure so you've got to plan for the future. In two years when the eldest hits year 6 you don't want to be diggin' your pockets again for the right desk.
Regardless of your choice i.e convential or computer desk, the more important purchase is a supportive chair to make sure they keep a good posture.
You could pick up quality computer desks and chairs really cheap from Greys Online. Some nice ex. professional office stuff. Mega cheap computers as well, but don't mention that to your other half.
http://www.graysonline.com.au/
Worth a try.
