If I were to do it again, I would not take new expensive outfits with us. Our daughter was 12 months old and I threw out brand new really cute outfits. On the 20 hour trip home she went through 4 outfits alone! We ended up wrapping her in a airplane blanket because I only had one outfit left and I needed something to dress her in when we got to the airport!
Pack lots of diapers!!! I packed what I thought was a lot for the trip home, but I was changing her every 1/2 hour for 20 hours (sometimes more)!! I was getting pretty nervous towards the end of the flight!
I went by weights and was pretty on. Our daugher was so small some things were a little big on her, but not bad. Our son was pretty short, so we had to roll his pants up for a little while.