Cute dog sweater, Katie! Have you tried to see if you can get the sweater stitches around a 16" circular? Even if it's 14" around, it will stretch. I bet you can get away with just doing the legs with DPN on that project. Definitely go with bamboo or wood for the first time DPN project if it's something with so few stitches as the legs of the dog sweater. You'd want at least 8-10 stitches on a metal needle to keep it from sliding out when you're getting the hang of DPN, more stitches if you're a loose knitter. But do try DPN, a lot of folks prefer them, including myself! Great advice on this thread from everyone, you'll be off to a good start. And having said Bamboo DPN, that's my advice to start, but as Sandy said, if you like metal needles generally, you may like them on DPN once you get the hang of them. I do my socks on simple Boye or Susan Bates metal needles.
Oh, and if you want to ease into sock DPN knitting, you might like Elizabeth Zimmerman's Moccasin Socks pattern, which has you do the cuff in the round but then the instep using flat knitting and a 16" circular. It's a great pattern in general, and uses half the DPN knitting of most socks. Even less actually, since it's in worsted weight yarn. The construction is unusual, so if you're looking for the classic sock, that's not it. Very practical and fun though!
KnittingHelp Queen Bee
It is not because things are so difficult that we do not dare; it is because we do not dare that they are difficult.