my uncle use to be right into this and my wifes uncle is right into as well.
my uncle is getting very old and passed it on to one of his sons, so what he did was he luckily had a shed with a open gable in the roof section and made a mezzanine with a few access service and play holes. he also cut the size of the set in half keeping the best parts and the other half sold off to fund the shed mods.
my wifes uncle modified a few trusses in the roof and put in a bunnings attic ladder ($300) so he could get in there easier and placed some yellow tongue down and has a new area for the grandkids to play, his old property had ride on train sets and track all through the back yard so he was real serious.
I reckon downsize and keep the sentimental parts so your kids could play in a modified shed mezzanine so you play the pinnies down below and kids in the rood section.
good luck mate
