C.R.
I agree with the bins...I would suggest canvas...not plastic(they crack)...but I would also suggest if you have part of your basement that they can't get into keeping bins of toys in there and rotating them every month or so...this help on 2 levels...clean up isn't so overwhelming because there is less to clean up and it keeps things new...I noticed when my kids had everything at their reach they made a huge mess but never really played with anything...now that I rotate toys, it's like Christmas for them every other month and they play better with each other and the toys...they will ask for the rescue heroes, so then we clean up all the trains and match box cars and replace them with the rescue heroes...and so on....there are a couple of things like the "kitchen" that you may not be able to move but you can pack up the food and dishes and put them away...I would keep toys at their level, but all games, puzzles, and thing with small pieces where they have to ask for them(top shelf of a closet)...again easier to clean up and keep all pieces together. Have fun!
ps...chalk board paint would be cool for a wall or a door...it's cheap and then they can draw on the walls!(this would also depend on the ages and supervision)