Beautiful!! You really MUST love the baby/family, to knit all of that on straights!! I tried knitting a heavy thick wrap on straights, and you're right, it just about kills your hands/wrists - aggravated my carpal tunnel syndrome.
Using circs for big projects, you just switch the needles at the end of the row and pretend that the 2 needles are straights, keeping the stitches on the cable - your lap will then support the growing weight, instead of your wrists. Please don't knit yourself into carpal tunnel! We want to see more beautiful work