The smaller one is from this kid sized messenger bag tutorial and was very fast to make! I added in a zippered inside pocket to that, just to give it a little something extra.
(Tiny strap is perfect sized for a 2-4 year old, might make it longer for my almost 5 year old if she wanted to wear it across)
(Used a 7" jeans zipper I picked up on clearance)
Be on the lookout for a tutorial for the bigger bags, along with more pictures!