There are a few units out there with mid bunks and a loft that would probably be similar. Or, Sierra and I think another one has a rear queen with a loft for a bunk house that would allow the kids to grow larger.
One of the issue I have with my bunkhouse is not having room for toys. We have a bike rack on the back, but 3 bike is max as the bikes get larger it is harder to fit them on. We have taken 4 but it's hard to get them all on. Small bikes and kids bikes don't attach to a bike rack correctly. I would think about toy haulers, just so you can give the kids a place to call there own, store bikes, kayak or paddle boards. You might upgrade to a quad or motor bike in the future or something. The toy hauler lets you grow.