Loft bed! Like this! Randy built a loft bed for Christopher years ago so when I suggested the idea to him-- which I did like I was suggesting we build a bed on a hoverboard-- he was all, yeah, okay. Shrug. I don't even think Chris's bed had a rail.
good use of space in bedrooms upstairs...especially given the small dormer/storybook windows...build in a twin, so room is open for playing, and then when they're older, this can be a reading/studying nook and they can have a larger bed in the room.