For the boys :-)
tented lofted bed
Image from http://1.bp.blogspot.com/-60yqSKlyYaw/UzgXGf7oOtI/AAAAAAAASxs/vtBTCXuMj1k/s1600/Rocket+ship+play+hut-space+theme+bedroom+fun+furniture.jpg.
Must do this for legos!
bunk beds...your Dad says he can build these!
Loft Bed | Do It Yourself Home Projects from Ana White
DIY PVC Pipe Fort. - Thinking about making a bed tent for Nathan, and this might be a good starting point to figure out what's involved.
Homelegance B2027-1 Castle with Tent Metal Loft Bed, Twin, White/Pink Homelegance http://www.amazon.com/dp/B00V5WVK3I/ref=cm_sw_r_pi_dp_lysqwb0PTBW63
Image from http://2.bp.blogspot.com/-DDYJ38SXefM/Ucx4hITgBeI/AAAAAAAAYvg/bb_vI-sVin0/s1266/whimsical_circus_tent_kids_tent.jpg.