I also run devcommands on my server, but you do have to be admin for it to work, so you'd have to give your kids admin rights before they can use them commands, My buddy and I do have working commands but the non admins on the server do not, you just need to add their ID into that list, can have them join the server and press f2 and I take a screen shot and alt+tab and type it all in. I had to add the devcommands because we had some guy on my server randomly teleporting and spawning in stuff and we want to play normal with a few little mods like Mass farming or dual wielding and that person knew before joining but didn't do as we asked.