They are knit flat so it doesn't matter what needle type you use. I used a 24 inch circular needle. It was too long really, but I was fine with them. The only thing you'd really need DPNs for is if you make an i-cord tie. I started to then changed my mind and just made a crochet chain.
Also...I was using DK weight yarn and wanted newborn size so I used size 3 and 4 needles. They look like they'd fit a newborn just fine.