I think it's a good idea as long as you restrict its use and invest in some really good educational software games which will help them develop their skills, rather than some of the mindless games which are available. It will also hopefully ensure that your valuable new computer doesn't get interfered with.
Just one thing though. Please don't let them neglect their reading skills and books. These too are very important, and if children are encouraged to enjoy reading when young, this will stay with them all their lives.