Hi,
Perhaps read a story to the children about a transition - new baby sister/brother, new home etc?
Get them to bring a comfort item from home? They could share around and discuss the story (depending on the age of the children).
Then they could each create a picture or do a handprint to put together and make a collage? Symbolising a setting which is a home from home? This can link into the transition session.
Observations are the worst, but just remember this is what you want to do (hopefully anyway lol), think more about the children and less about the assessor