I had a similar problem with one or more previous children, but the bundle outfits (no legs) are usually sized up to 18 months, and Frank is too big.
He stayed under his blanket during his nap, because he was so worn out after Mass, and he was warm when I picked him up.
The bundle outfits my son was in were like one-piece feet-jammies, with a zipper, but made of fleece. They were a life saver to me!