I'm not seeing that as a good visual blend with the rest of the house unless you can go bigger.
I think, though, a vertical siding (T1-11) might be a better match. A more dated look, but I think it goes better with your house.
JMHO

I love modern architecture, but I really am not a fan of the translucent garage doors. I've seen them on several projects and they haven't won me over. One loft style building here has them, but they used clear glass, and you can see all the tenants belonging and can tell if they're home or not by whether or not there's a car in the garage!

Back to the point though, your house doesn't have any flat roofs (excluding the carport, which is an add-on). Why not go back with a roof at the same pitch? It would blend in more I think.

Have you verified your allowable building setback to know if you can even add on a garage there? Just because a carport was added there doesn't mean it's in compliance.