I've never sewn my own, but for your cover I would suggest either a double layer of fleece, a single layer of PUL or PUL on the outside and fleece on the inside - it's hard not to get cotton to wick. If you are making flats to fold into the covers I would definitely do gussets esp. with newborn poo. http://www.kamsnaps.com is a popular place for plastic diaper snaps. I have a pair of their pliers and repair our bumgenius diapers during car trips! After replacing A LOT of worn out velcro/aplix I prefer snaps. I've also repaired some elastic and instead of sewing the entire thing, sew both ends and then sew along the outside to make a channel (but maybe that is only important for OS diapers?) Congrats on your expanding family!