Bunk ladder/safety rail

You could stick a pool noodle under the mattress pad along the exposed edge. Our kids wanted to sleep with their heads pointed into the bunk so that could be an option too. To some degree it depends on the personality of your kids. Our oldest has been in a bunk bed since around 5 at home but she's the kind of kid that will follow instructions without fail so we gave her a few safety guidelines up front and she never wavered on them. Our middle kid is different and will test limits all the time. Time will tell where the youngest falls on that spectrum.