My friend asked me how did I keep my house clean and tidy the whole time although I have 3 active sons and I am SO pregnant?
My first question would be : Who told you that?
It is normal for the kids to create a mess in the house. That is the beauty of being a kid. They need to play, explore and learn new things. Let them imagine. Let them learn. Let them create the mess.
And get them to clean up afterwards.