They look off and somewhat disturbing because they're poorly drawn, that's all. Nothing sinister about it, it's their first book and it shows. I say, I'm not seeing any signs of a great literary career for the author, nor great art/illustrating career for the guy who drew the pictures. This whole book looks average, it's subject might seem controversial to some, but given how open we are beginning to be to children about various things, I think it's nothing unusual. I've seen worse illustrations, more controversial (and gross, to boot) topics and worse writing than that. I've also seen a lot of better ones. It seems low-average to me, the author is clearly medicore, but to his credit, he's not aiming for the heavens, either. Not much else can be said about that, really, as it's pretty short and somewhat bland, as usual with children books.
Oh, and there should probably be a children's book on gun safety, too (if there already isn't). When you first introduce anyone (young or old) to firearms in general, the first words they hear should be about safety. No matter what your political/moral/etc. stance on guns is, it's imperative to know the basic safety rules before you're within a meter of a functional firearm (or even an airgun, or an ASG replica).
As for the concept of open carry, I have no problems with it. Concealed carry is fine, and very useful if you want to look snazzy. A gun holster hardly looks good with anything except cammie trousers (well, OK, cowboy trousers could work, too, but only if you're from Texas

), and the only ones that look remotely "snazzy" are MARPAT ones, which aren't permitted for casual wear in the US anyway (what with being the current USMC uniform pattern). If you don't care about looks, open carry is more "honest" (in that everyone sees you're armed) and it's much less prone to snagging issues. A good holster can allow the gun to be drawn very quickly (much faster than most concealed carry options), meaning any would-be attacker stands a little chance of stopping you if you practice this enough. It's also safer and allows more flexible choice of your weapon.