I guess it depends on what your child is used to. if they have games consoles and access to a real PC, I dont think that one of these is likely to hold their attention for long. Without experience of the other things, they may get more enjoyment.
I have an 8 and a 7 year old and my 8 year old is also after a laptop, but I know that one of the educational ones you are considering would not cut it. So, he is not getting one at all until I feel it is appropriate (and we can afford) to get him a real one. Some of the vtech ones are around the �100 mark and do look the part, but I think for a child used to using windows and a real screen, you may soon feel the limitations and the fact that you cant really enhance it or get extra software - that's a lot of money to gather dust.
What about buying a 2nd hand real lap top with software, but no internet access?