The baby kind work well for me. My favorite modern baby diaper pins are the Dritz brand. You can get them from Changing Times or just about any company that sells cloth diapers for babies.
That said, though they're available in various pastel "baby" colors, they're not super babyish. My all-time favorite diaper pins are true vintage 50's/60's/70's baby diaper pins with the duck-, chick-, and bear-shaped heads. And there are many other shapes as well. These old pins are not only cute, but have very sharp points and gradual tapers that make pinning a breeze. I especially like the Reddy brand. Keep an eye out for these on eBay, as you'll occasionally spot brand new packages of them. Used is often fine also. I've collected well over 100 of these old pins and they're absolutely my go-to pins.
...but beware the look-alike Chinese pins from the 90's and after. You'll often see these selling on eBay in large bulk lots and claiming to be vintage. If the image shows dozens of the same pin and no packaging, stay away. They're garbage. Also anything with "novelty" on the package is definitely from the late 80's or later, and will be of poorer quality.