I finished the matching blanket this morning. It wound up 34 x 46 in size.
I found that working with the thinner flannel is not easier than working with fleece. The fleece is very forgiving when you go in a line you don't particularly like. (Had to back up and use the seam ripper once or twice) And the back of the fleece looks nicer when it's all finished. I could always double the flannel, but I don't want to make it too heavy, since it's meant for a receiving blanket, not a heavy one. Most embroidery has some kind of scratchy backing on it, for stablization. I'm afraid it would be too rough for a baby, so I'll have to come up with an alternative.
All in all, I'm fairly pleased with the result and I hope the new mother likes the set.