It won't take them long to learn how to do them at that age if they don't know already. Velcro is easier but snaps teaches them how to line up the parts to close..

I would use both to give them different experiences. Apologies if I have got the question wrong/ misenterpreted it. Are you asking for assembling the book or the content of a page?

I think Kam fasteners would be fine. They are starting to learn to dress themselves and their fine motor skills are developing. Just make sure the fasteners aren't easy to pull out of the fabric. Definitely use Velcro for under age 2 or for children who have motor skill issues, such as children with Cerebral Palsy. Hmmm, there's a whole new area for our folks who have booths to sell their items. Include a few items for children with Special Needs.