[ChromaKelly]

I don't think an 18 month old really understands that much of Mommy needs to change clothes and all that yet. It seems to work much better to have a little bit of a warning time of a transition and to somehow keep them occupied when you have to do those necessary things between activities, like go to the bathroom. I'm not above giving a little snack or turning the TV on so I can run to the bathroom, throw some clothes on, etc before we leave.
As for transitions (the classic carrying a screaming toddler away from the playground scenario), it helps to give some warning and making the leaving time absolute. Three more pushes on the swing and then we are leaving, and count it down. If they know they can whine and cry for more time, they will do it.