Thinking 'it's bollocks' is a normal part of the process. If you spent the entire first draft thinking 'I'm writing the most amazing prose ever,' you'd probably be wrong. Good luck, I hope you finish (says she, who is writing this response rather than getting off her lazy backside and finishing the last few edits of her novel...)
It is a children's novel, aimed at about 11-12 year old readers. How many words? Myselxia suggests 30,000. I don't want to make it too long as I would like it to be a school reader (ha ha ha - how ambitious am I???!!!).
I know what I'm going to write - vaguely - so no problem there, just doubting myself. Again. It's why I've been faffing about for the last decade rather than just getting on with it and putting it out there.
I am also notoriously bad at finishing anything. I want to do it for that reason alone!