All done - after the big decision making process with the buttons, at the last moment I found two little olive green buttons at the bottom of my button box and realised that they were perfect.
I crocheted round the whole neck opening and made two loops as I went for buttonholes.
The pattern is Little Sister's Dress by Tosa Froseth.
The yarn is RYC cashcotton 4 ply in citron (the colour is better in the second photo).
I used a 3.25mm addi lace circular needle throughout.
I used a 2.5mm crochet hook for the neck.
My row gauge was a little off so I made a few modifications to account for this.
This project has reminded me how much I love RYC cashcotton 4 ply. It feels beautifully soft and wears and machine washes well so should be good for baby clothes. It has been discontinued now so I've been online in the last week, scooping up as much as I can from the virtual bargain bins. I now have a nice little stash of it for baby jumpers and socks and the like.