Sorry, I did not address your specific and clear concern. I wasn't paying close enough attention.
Salmonella exists in the world. It is certainly possible that our chickens live in areas that have it. If you have a dog that spends any time out of doors it could have salmonella in its fur. There are lots of things that can infect you with salmonella.
If you read up on it you will be told how common it is and all the risks. It is pretty common in the world. Practically any case of food poisoning you hear about is caused by salmonella. Some people are more vulnerable than others, the very young, old, or people with compromised immune systems. Many get over it on their own but it can kill. The general preventative is cleanliness. Keep animals out of your food preparation areas, be careful handling raw meat, rinse off your fresh veggies, fruit, or berries before you eat then raw, cook things properly, and wash your hands a lot.
That's the general stuff. Now your specific question, will leaving the eggs unwashed on your counter give your grandkids (or you) salmonella?
Are you going to let your grandkids handle the eggs or cartons if they are in cartons? If they do have then wash their hands before they stick their fingers in their mouth or eyes or pick their noses or wash their hands for them yourself. I have a 4-year-old grandson, try teaching him not to pick his nose.
Wash the eggs before you use them and wash your hands. Cook them, don't serve them raw. Doing these things should pretty much eliminate the risk from salmonella.