I don't think he's using emuNand - btw keldog, EmuNand is a virtual OS installed "inside" your current one. Using that, your system will stay on 4.x but you can go into 7.1 to use eShop and full wifi. But, it's a little difficult to use and the wrong move could ruin your system, plus you have children playing on it so I don't think it's the best idea. I would recommend making sure the wireless is never on outside the house - as others have said, Bestbuy, McDonalds, etc provide "Nintendo Zone" - a free network in which the 3DS can connect to and download updates.
If you keep wireless contained home, you should be good to go. The only issue would be soemthing very rare - a neighbor sets up "HomePass" which is a Nintendo Zone inside your home with some other features. If the 3DS's find that fake Nintendo Zone, they can download the update from there. To check for a nearby HomePass network, use a wifi device or something to search for nearby networks. If something is named the_Cloud or attwifi, it's a Homepass network.