What's an RE?
My biggest suggestion would be to think about not only what might work for kids ages 2-9, but also a few years down the road for kids (say) aged 7-14. Some of the bunk models have bunks that are pretty short, and a tall teenager (or adult) would definitely be cramped by that. At least for me, while a wide bed is nice, a long enough one is an absolute essential.
It might be worth at least peeking at some class C's as well as trailers, too. The cabover bunk does work out nicely for kids (and is a sort of hidey-hole that many of them like to have).