Have you used prefolds before, like for sizing comparison?
I would think that the regular size would fit them both (roughly 14.5 x 21 new, I think). That's just a guess though.
The beauty of making your own is you can make them any old size you want!!! If I were doing it again, I would want a little wider and a little shorter, since my ds is sort of petite and a lot of babies outgrow the width before the length.
Check out greenmountaindiapers for a lot of size options.
Really, any fabric will work! Even old flannel sheets or pajamas. Flannel is nice because it's so soft. But I like to be able to use a snappi and you can't with flannel. Birdseye would be nice for that. Or 100% cotton terry on the outside would be nice for that, too. You can snappi them both. If you look online you can even find luxury fabrics like cotton velour or bamboo. Really, you can go as cheap or expensive as you want. Whatever you use, I would make a few and test them for size, absorbancy and drying time to see if they work for you, then adjust as needed!
Christina, Mama to Salvador (3 yr) & Santiago (6 mo)! www.footprintsbaby.com Life has gotten too busy - Come shop our going out of business sale! Cloth Dipes & more.