The intarsia sweater patterns Sheep & Reindeer and Sailboat & Whale are written for child sizes 2-12 in worsted weight yarn. Katherine's recommendation: I really like Ultra Wool for children's sweaters. It comes in many beautiful colors, is a pleasure on your needles and is (gently) machine washable, lay flat to dry. For more of a summer weight, Modern Cotten would be a wonderful choice.
The Baby sweaters, hats & blankets pattern is sized for preemie to 12 months, also in worsted weight yarn. Katherine's recommendation: Modern Cotton or Comfort would be excellent choices for this pattern.
The Classic Christmas Stockings are worked in a heavy worsted or bulky weight, and have a finished length of approximately 25". Katherine's recommendation: the Deluxe Bulky wool would be beautiful for this pattern.
The Classic Sock pattern is the one sock pattern every knitter should have. It includes babies through men's sizes in fingering, sport and worsted weight yarn, making it endlessly versatile. It's also very clearly written so even a sock knitting novice can follow along! Katherine's notes:your greatest durability will come from yarn that includes some nylon; most yarns designed for socks will be roughly 25% nylon and 75% superwash wool - it's a winning combination. You certainly can knit socks from 100% wool, but if they are worn a lot, watch for wear on the heels and toes, and do be mindful of washing instructions.