My Easter Eggers are really sweet, and they lay really nicely colored blue and green eggs, which your kids would probably think is really cool.
Orpingtons are known for being really docile, and good layers. They don't really mind being held, which is nice for kids.
"Red Pullets" are readily available at almost any feedstore such as
TSC or AgWay during the spring, and are friendly and lay big eggs every day. These can consist of Red Sexlinks, Rhode Island Reds, New Hampshire Reds, and others. Mine love their snacks and sometimes jump up on my shoulders when I am feeding them. They're not being mean, they're just really excited for their treats, but that kind of behavior might scare really young kids. However, I was able to break them of this habit, so they can be trained not to do this.
Silkies in my opinion are really the nicest chicken out there, but only lay 3-4 days out of the week. They have cute little pink or cream colored eggs. My silkies are by far my favorite kind of bird even though they don't lay well.
Wyandottes are really pretty and mine don't mind being held at all. They lay well, and get along with everyone in the flock, even the small birds like my bantams and my silkies.