I probably wouldn't bother and just call him Noah.
If you're a nick namey family then he'll likely get an organic nickname to do with his personality rather than a shortened name
I think I would automatically go for noh-noh if it was me but you will find the nick name when he is here it's just one of those things!
I have a Noah and he’s baby Nono. Now he’s a toddler it’s funny trying to say no 😝
My little cousin is a Noah, and everyone just calls him nor, idk why😂xx