A cheaper idea is to get some canvas and paint from the dollar store and put some paint on the canvas, put it in a zip lock bag and let her push the color around too "paint" him a picture
More expensive idea would be the day and me book or a bear made out of her first outfit
I did foot prints to make a balloon bouquet canvas art from his son
I have a few ideas on my LTK. https://www.shopltk.com/explore/FunWithTheJohnsons/productsets/11eee61bdab961b0a6da0242ac110023
There are lots of ideas on Etsy. I got my husband a key chain with the name and birth stats of both girls after they were born but there are lots of ideas on there