Interesting idea, but sadly it doesn't work. I don't believe in Dr Ward's theory there is any logical sequence to the order in which he says Lewis wrote each book around, except i seem to recall that he says that Jupiter (LWW) was first since this was the planet which fascinated him the most.

In Publication order it would be:

Jupiter: The Lion, the Witch and the Wardrobe
Mars: Prince Caspian
The Sun: The Voyage of the "Dawn Treader"
The Moon: The Silver Chair
Mercury: The Horse and his Boy
Venus: The Magician's Nephew
Saturn: The Last Battle

In Chronological order it would be:

Venus: The Magician's Nephew
Jupiter: The Lion, the Witch and the Wardrobe
Mercury: The Horse and his Boy
Mars: Prince Caspian
The Sun: The Voyage of the "Dawn Treader"
The Moon: The Silver Chair
Saturn: The Last Battle

In neither order would the planets be arranged into any sort of sequence.

Out of curiousity, has anyone else on NarniaWeb actually read Planet Narnia? I found the book to be quite an interesting read, even though I am not 100% convinced that C.S. Lewis meant to write the books with the attributes of the planets. Do you find Ward's argument convincing? I'm looking forward to his book for children and I'm hoping he's found more evidence to support his claim.

*Edit
I went to the Planet Narnia website and found this under the FAQ section:

Does this discovery affect the order in which the books should be read?

No, though it reinforces the primacy of The Lion, the Witch and the Wardrobe. Lewis wrote his Jupiter story first because Jupiter was his favourite planet, the one that he thought was in particular need of imaginative rehabilitation, and the one that was connected with the ideas he had expressed in his previous book, Miracles. When he began writing The Lion (1948), Lewis did not intend to write more than a single story, but he soon changed his mind. From Jupiter (the sixth planet, Fortuna Major), there was no very obvious planetary order for Lewis to pursue. However, it would have seemed natural to move from Fortuna Major to Fortuna Minor (Venus - The Magician's Nephew), and we know that this was the next story Lewis started to write. It was also a natural decision to finish the series (once he had decided on writing books for all seven planets) with Saturn, the last planet, which he did.

The Lion, the Witch and the Wardrobe was not only written first, it was also published first, and the way that it introduces Aslan indicates that the reader is not expected to know who he is, whereas The Magician's Nephew (even though it deals with an earlier period of Narnia history) does not take particular pains to introduce him, because Lewis knew that most of his readers would already have encountered Aslan in earlier published volumes. The Magician's Nephew also expects that the reader knows about the magic wardrobe. For these reasons (among others), it is a mistake for publishers to put the number 1 on the spine of The Magician's Nephew or to print it first in multi-volume editions.

It ought to be remembered that not all the books were written in the order they were published. The Horse and His Boy was written fourth, but published fifth. The Magician's Nephew was begun second, completed seventh, and published sixth.

Clearly, when someone reads the series for the first time, The Lion, the Witch and the Wardrobe should always come at the start and The Last Battle at the end; Prince Caspian should be read at some point after The Lion; The 'Dawn Treader' should be read at some point after Prince Caspian; The Silver Chair should be read at some point after The 'Dawn Treader'. It does not particularly matter where in the series first-timers read The Magician's Nephew and The Horse and His Boy as long as those two stories are read after The Lion and before The Last Battle. My own advice to first-timers is to read The Magician's Nephew and The Horse and His Boy, like the whole series, in the order of publication, which is this:

1. The Lion, the Witch and the Wardrobe (1950)

2. Prince Caspian (1951)

3. The Voyage of the 'Dawn Treader' (1952)

4. The Silver Chair (1953)

5. The Horse and His Boy (1954)

6. The Magician's Nephew (1955)

7. The Last Battle (1956)

I hope that helps!