Splitting a five frame nuc seems like a bit much in my opinion. Maybe split the overwintered hives into four hives and set up the five nucs. All nine colonies would be similar sized. Run those nine hives for a while to see how they grow. Order some mailorder packages in a couple months if you want to increase to 15. A late May package with a donation of a frame of brood or two should overwinter next year nicely and you'd stand good odds of honey producion from the first nine.