Spend the Day Together
You also might want to consider having the babysitter spend the whole day at the house with a parent present. This can help the babysitter see the family routine, and it helps to further cement the bonding time.
A Trick With Toys
There is another thing that might help, too, and it involved a trick with a toy. No child likes when things are inconsistent, and it can make them feel uncomfortable when in these situations. If they know what is happening, they can prepare.