I give my girls scrambled eggs and occasionally, boiled eggs. It's one of their favorite treats, and I haven't had any problems with them becoming egg eaters...knock on wood. They are definitely a good source of protein for them. I also like to crunch up the eggshells after I've cooked the eggs and spread them around in the run so the girls can forage and get a little extra calcium. They also love watermelon and heads of lettuce...but I digress.
As far as buying hatching eggs and having them shipped in the mail, I've had mixed luck. A lot of it really depends on how rough/gentle the postal service is with the eggs. Just make sure to let the eggs "rest" for 24 hours with the large end facing up so that the air cell can get into the correct position before putting them in the incubator. I like to candle my eggs when they arrive so I can see if any of the air cells have become detached during shipping and check for any internal cracks that aren't visibe to the naked eye.