In my experience with my little flock of 12, they will be totally fine with kids! Guineas are a very wild bird, SO different from the domestic chickens and other fowl you are used to. They will steer clear of humans for the most part. Mine trust me enough to come near me (to see if i have treats haha!) but one quick movement and they scatter. They are not a friendly pet bird at all, but they shouldn't attack you or your kids
Just be sure to do research to make sure they will fit in your lifestyle! They are such funny, awesome birds (and great at tick control!) but they are loud, and very hard to handle compared to chickens. They require training to get them to come back into a coop at night, and you can't really catch them easily if you need to move them or something like you can a chicken. And i don't know how big your yard is, but they will not stay in a little yard, haha. They like to move, and mine range around 10 acres of my land, and neighbors land. One second they are on my back porch, and then not even a minute later i hear them scream at the neighbor's dog as they are chased away from the bird feeder! I still shocks me how fast they cover ground! lol
Hope this answered your question! And good luck with your little chicks this year!