I'm pitching in with the others - get the 560 with the bunk beds for your little ones. The four year old will still climb in with you 'cause that's what they do (and sleep sideways, shoving those sharp little toes into somebody's ribs). Besides, why would you really want a king size? As Jim would say, "There's too much room. I'd spend half the night chasing you down!"
Gotta love that guy.
Camp On,
Sue (sore ribs)