Hi Megan,
Honestly, I’ve never heard of GFI. That being said, a couple things you should be aware of I guess.
First is that the outlets here are circular and narrower, so you can’t get a knife or a fork in there. Maybe a shishkebob skewer, but I’d be worried about the skewer poking out an eyeball first 😉...
Second is that, in general, Spain doesn’t have many safety features on anything. Dangers lurk everywhere if you’re looking for them and it seems like the attitude is very much, “life is a risk, let’s not waste it worrying about the little things”. So you won’t find smoke detectors in your house or child-proof balconies, and I’ve been stuck in elevators that mustn’t have seen a repairman or inspector in a decade (in fact one of them is in my own building. Reassuringly, they’ve installed two giant springs on the ground floor, in case…?). Life is just, well, more raw here, but people learn to use common sense instead of relying on bureaucraticly induced safety features. I’m sure your kids will too!
In a pinch you might be able to find what you’re looking for at El Corte Ingles or in your local ferreteria (hardware/tool shop).
Welcome to Spain!