It's bit dicey. Both are located at distance and traffic plays role here. Old goa can be covered within few hours but getting back and covering north is not possible. In my suggestion you can go to old goa cover the places and be back by afternoon to cover one or two places in North along with sunset at any good beach. Or you can either skip old goa and utilize your time entirely in North part, it won't be enough but you can cover many places.