Hi Susea, It's quite hard to picture it as a graphic novel, so I'm not sure how helpful what I say will be.
Firstly: Love the concept, Children love Dodos and mysteries so that's a great start.
A few things that occur to me reading it, but a lot is personal, so others may disagree. It's not that I'm picking on the story, just things for you to think about for editing.
1. I'm not convinced by the introduction. It might work addressing the reader when put into graphics, but I think my children at that age would have found it cringy.
2. When you "make their names easier to say" I don't think at that age they will find "Psitta" easy. Tbf I'm not quite sure how you would want it pronounced. Why don't you have one of them pronounce it carefully (Like Hermoine does at one point in Harry Potter) or make a joke about it rhyming with something etc.
3. I think you could bring in humour in at times. Things like the bit about ghosts:
"PLATE 2
NESO speaks to the reader.
NESO: Did you know that some scientists studying ghosts believe there is a link between
mould and ghosts?
PSITTA: When enough mould grows thick enough, this can make people hallucinate.
PLATE 3
NESO looks at the reader.
NESO: Or see things that aren’t there."
Make it funny. Have Psitta make him jump or pretend to see something and scare him.
4. I don't get a real sense of characters with Neso and Psitta. Give them some defining characteristics. This may come out with the graphics, but I think to be able to read a speech and know who said it would be what I'd be looking for Have one of them the questioning one, and the other knowledgeable, or one more cautious, or something that makes me feel I know them as people, at the moment I don't feel I know them.
5. This may be graphic novels, but the episodes feel really quick. I'm just reading a bit and thinking "interesting" and it moves on.
6. I love the bits where they're reading from the books. I can really picture those.
I think there is a lot of potential here, but it is hard to visualise it without it being put into graphics. Do you have an artist?
I don't know if you've seen the Walking with Dinosaur DVDs? My son used to love them - they were done like nature documentaries but with dinosaurs, and this is kind of the vibe I'm getting from this. I think he'd have enjoyed this story at the right age.
Hope you don't feel I'm being negative, I did enjoy it and think there's a lot of potential for a fun story for that age.