I make a baby quilt for each great niece/nephew that is born. The top is pieced flannel and the back is a minke type fabric. It has plenty of body already but I do use white quilting fabric as the batting. The reason I do this is because I think that the flannel and minke both stretch and if I didn't put that stabilizing fabric in the sandwich, the quilting stitches would tend to break from the stretching. Just a thought for you. Although, you did say your top was normal fabrics so your situation is not quite the same as mine. Good Luck!
BTW - I prewash all fabrics in hot water and dry in a hot dryer. I assume parents will want to use these temps when washing the quilt so I want to be sure there are no bleeding or shrinking issues.