One classic sentence starter could be 'In the dead of night, a strange noise echoed through the empty house.' It immediately sets a spooky mood as the 'dead of night' implies a time when most people are asleep and vulnerable, and a strange noise in an empty house is often associated with something sinister.
A great starting sentence for a story might be 'The day began like any other, but little did I know...'. It creates a sense of normalcy at first and then hints at something unexpected to come. This type of start draws the reader in as they want to find out what that 'little did I know' part is all about.
Well, 'Long ago, in a different world...' is a great sentence starter for a story. It makes the reader think about a time and place that's not the present. 'Suddenly, everything changed...' is also good as it grabs the reader's attention right away, making them wonder what changed. 'There was a small town where...' is useful for setting the scene in a more specific location.
Some good sentence starters could be 'In the shadowy recesses of the old mansion, a strange silence prevailed...' or 'The howling wind whipped through the desolate graveyard as...' Another one could be 'Amidst the thick fog that cloaked the ancient forest, a figure emerged...'
Try 'In a far - away land...'. It takes the kids to a different place in their imagination. They will be excited to know what is in that far - away land. It could be a land full of talking animals or magical castles.