You could go down to even a Cat 9 - as long as you don't want the verandah. The beds are "bunk" like in that the sofa turns over (it's the coolest thing ever per my kids) into one bed and the upper bunk comes out of the ceiling. There is a weight limit on the upper bunk but it's about 160-180 so I have a feeling you'll be ok there too.
We cruised in a Cat 6 the first time and liked the verandah, but didn't LOVE it. We booked a Cat 9 the 2nd cruise and I was a bit worried at only having a window. But boy, *what* a window. It was perfect and we honestly didn't miss the verandah at all. We spend very little time in the room - the first cruise the kids napped some, but rather than be on the verandah, we slept too (lol). The 2nd cruise, we were there to change and sleep and that was about it. We take the savings from a Cat 6 to a Cat 9 and use it for "fun" on the cruise!