I got mine at Old Navy, but you can find similar boots at Target, Walmart, and other stores. These are boots that children will wear without shoes; one tip is to buy a bigger size in the fall so they can wear two pairs of socks during cold/snowy weather. By the time summer rolls around, they should be comfy going barefoot in their boots!
Pros: Can walk through any wet/nasty substance without getting shoes or pantlegs dirty (if you tuck pants in or roll them up). This means that dog poop, mud, and other yucky things stay on the boots and at the door instead of being tracked in your house! They're also fairly easy to take off, facilitating removal at the door. Go puddle walking with flair and with no worries!
Cons: Can't think of any except that the fabric lined ones take a while to dry if water gets inside (like, um, if a well-meaning 2-year-old pours a cup of water inside while they're perched by the door...).
Well worth the investment. They hold up well, enable your kids to play outside in all kinds of weather, and are easy enough for the kids to put on by themselves. If you make the investment for your kids, you should get yourself some! Who's going to be going puddle jumping with them?