I think your friend's son KNOWS those two shots with the hat are going to be embarrassing in later years
So in the first (1), he's turned a bit green (as Gill says) and in the second (5), his expression isn't great.
No 3
is a great expression, well captured, but I'm a bloke and I can't be saying I like the pursed lips look
Generally prefer the on his tummy/crawling shots (2, 3, 6 and 7), but that said, no doubt his Mum likes No.4.
He's looking tired by No.8.
Does your friends home have a photo studio?
Good place to shoot with uncluttered backgrounds.
Well done,