I'd say a Troll for the interior space for when the weather is poor and you need a bit of internal space as the awning is down. On a 530 the front is a 4 snug seater diner will make up to a double bed that the 10 & 13 year old could share for an odd night, but to be honest they will want to be out of the van. Ours went into pup tents at about 10 and loved there own space.
We prefer a fixed bed at the back. The extra height makes it more bed like and the space underneath is great for larger and lighter items.

Colin