if i have access to the head of the baby/person (like you do), i think the easiest thing to do is a universal fit-as-you-go idea/pattern.
1. measure the baby's head
2. do a swatch to get a per inch gauge for your particular yarn and needle. for a hat, a very small swatch will do. 10 stitches stockinette for 5 or 6 rows should be enough.
3. multiply the head circumference by the stitches per inch, and cast on the closest number of stitches to the stitch pattern you want (doesn't matter w/ stockinette, but divisible by four for a double rib, for instance) onto a circular needle. use a short needle and bunch the stitches on. i have started collecting the shortest needles i can.
4. knit til the hat is long enough that it would cover the "fat" part of the head (before the head starts to taper). easy to do when your model is right there.
5. then start to decrease:
K2TOG, knit 8 for one row. it's ok if you have fewer/more stitches left at the "end" of the row, that is fine. you can decide how to incorporate those in later rows.
knit a row
K2TOG, knit 7 for one row
knit a row
i do this all the way down to K2TOG, knit one. fits beautifully every time for me.
6. KTOG all the stitches in rounds until you only have one loop left. cut a tail, thread it through the last loop, pull it tight to form a knot.
7. turn the hat wrong-side out, pull the tail through, and "sew" the it into the knitted stitches of the hat with a tapestry needle to hide it.
some notes:
at the beginning..... if you want a rolled edge, do not use a ribbed band, but if you rib, do that for 3-5 rows, then plain knit. or, if you want a folded band, do the ribbing rows til you eyeball enough for a nice fold before switching to just knitting.
If you do NOT have a the baby there and aren't sure how tall the head is, you can throw in xtra knitted rows between the decreases to make a tapered, pixie-style hat, which you can shape as you go. very cute, and basically takes out the difficulty of fitting the hat properly.
i keep various lengths of circular needles on hand. if the work gets too stretched for the needle i'm working on, i slip it onto a shorter one to avoid DPNs. don't know how short you can get a circular with fat needles though! if you need to switch to DPNs as you decrease, just spread the stitches out as evenly as you can, and keep counting.
BTW, i am VERY a basic knitter. my first hat was my second knitting project, and i did it this way after reading many hat patterns. it makes total sense in my head... i do mostly hats, blankets and scarves, but a LOT of those. so, i love simple "patterns" and things that make for easier knitting, like the new super-short turbo circular needles that have pretty much eliminated my DPN knitting! yay!