>Also my kids share a room and they don't have enough space to play Lego without having to put it away at the end of the day
Having a safe spot for the soldering iron sounds like a good idea, but as far as putting away legos goes ... do you really want to teach your kids not to clean up after themselves? Those sorts of habits spill over.
Always putting things in their rightful place has been one of the most important lessons I've ever learned. That way your place is always tidy and you never have to explicitly do any tidying up.
There's no rightful place for a multiple-day build that hasn't been finished yet, though. You can't build complex stuff if you have to start from scratch every day.
The solution when I was a kid was a loft bed, it really saved a lot of space in my fairly small bedroom.
Having a safe spot for the soldering iron sounds like a good idea, but as far as putting away legos goes ... do you really want to teach your kids not to clean up after themselves? Those sorts of habits spill over.
Always putting things in their rightful place has been one of the most important lessons I've ever learned. That way your place is always tidy and you never have to explicitly do any tidying up.