The London Eye is fun for the kids, and for the parents it offers a nice way of keeping them amused while you can sit and relax for 30 minutes in your pod. I recommend going after you've been in town a bit so you have some idea of what you're looking at.
One thing to note is that the line-up for tickets can get HUGE. Plan on going early. We followed it up with a boat trip down the Thames to Greenwich (there's a dock just below the eye). This is a great thing for slightly older kids (although under 8s would probably languish) as there is SO much to see, and you get such a different perspective of London from here. We took a tube back into the city afterwards, as the same boat trip back would have lost much of its charm

QUOTE(inasia2008 @ May 29 2008, 11:31 PM)

The London Eye would be a good one for children