What is best style for two girls, ages 3 and 8?

I'd like a twin over full, transitional, and straight ladder on the end so it is out of sight for the toddler. A detachable option would even be nice, but I'm not sure if they even make that? Is there anything else I should consider? I am a single mom and this will be quite pricey so I want to make sure I've gotten exactly what we need.

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