C.O.
A.:
Limit the "stuff" the kids are allowed in the car(s). You will be surprised at just what they DO NOT need.
For their rooms? I will assume (I don't like to do that) that before you moved you got rid of the toys and things they do not use anymore. I don't know the size of the rooms and what you have available.
here's what I did...my kids rooms do not have toys in them. I know - sounds harsh - but this way - their rooms stay organized and we aren't stepping on soldiers, etc. Yes, they take toys to their rooms to play - but they don't stay in there.
If you want them to have toys in their room(s) then buy baskets or the rubbermaid tubs for them to store them in. The tubs are great because they can stack them.
Getting rid of the clutter is what helps me stay organized.