I revise my opinion, now that I have looked at the correct floor plan. I am sorry, I was looking at the 17 ft version. 21 ft for the 4 of you would probably be perfect. We had a very similar 24 ft layout, minus the slide out, for 2 of us. It was more trailer than we needed but if we had had 2 more people we would have wanted that extra room.
It got to the point that I hated the side mount bed. Hard to make and someone has to crawl over their partner to get out of bed. I assume young kids can climb in and out of the top bunk, I never slept in ours and I am not agile enough anymore to get into it.