How disruptive is it for a three year old to change classes?

[EttaJames]

DS1 has the opportunity to move from afternoon to morning session at kindergarten. Morning session is more practical and fits better with our DD's schedule, but I am concerned as he has a number of friends in his current class (has been there eight months). How close are friendships at that age, and is he likely to be confused and miss his afternoon class friends? TIA for any advice