I've been picking up the boys from daycare again

The younger one is 5 and a half now and going into kindy in September. One of the best things about that age is it provides such fodder for amateur armchair linguistics! (Linguistics is probably the only scientific field that sees more progress rather than less when its professionals become parents.) Today I caught him using a double modal: "We might can't walk fast, we should take a bus." (Nice try, kiddo, but your little legs can manage a ten minute walk.)

Are double modals common at his school/daycare? Or is he neologizing them because he's five? I haven't heard his mother use them, but maybe she does when she's at home? I have no idea, but now my ears are perked up and listening closely!

Also, I rather ambitiously offered to pick him up early and teach him how to read (or at least get him started with proper phonics) this summer. Wish me luck.